Boost leaks cobb acesses port tuner 18 pounds  now i think theres a boost leak it wont hold 18 drops to 12 then goes back up 18  dont no why

Fuel pressure may drop due to a leaking injector or bad check valve in the fuel pump itself. The regulator does not come into effect until the engine is running and a vacuum supply is produced to it. If the regulator is leaking internally, it could send fuel back to the tank as well. Prime the fuel line and pinch off the return line ( if possible ) to eliminate a regulator problem. If the fuel pressure drops with the return line pinched off, suspect a leaking injector or fuel pump. If injector is leaking, the vehicle should run rich and cause a hard start/rough run condition

Hello and welcome to Fixya.com
have you run a fuel pressure leak down test? if not you need to do this test, borrow or buy a fuel pressure test gage, they are about $12 at Kragen, the fuel pressure test port is on the top of the engine in the fuel rail that goes over the injectors, looks like a tire valve, hook up the gage and verify you have no leaks, then start the engine and turn if off while watching the fuel pressure, the pressure should not bleed down by more than 5 pounds after engine stops running, if it quickly looses pressure u will need to replace the fuel pump, this is called a leak down test, fuel pressure leak down is the #1 cause of hard starting rough running cold, other things cause it as well like a loose timing belt and worn out plugs and dirty fuel injectors, and worn engine parts, but start with the leak down and then go from there.

Go to your local auto parts purchase a a/c charge kit for about $69.00, find the low pressure(suction) fill port, there are two ports in every a/c system one is a low pressure side used primarily to fill a system with freon 123a or the like and it is the larger valve mounted on the line, then there is the dangerous high side valve, this is a smaller diameter valve mounted to a smaller diamet a/c line, this is under extreme pressure so donot attempt to fill this high side with freon as it can backfire on you and cause injury.
The low side fill kit will not fit on the high side port so thank godness for that.
start the vehicle put the a/c on full cold high blow fan speed, start filling the low side with a can of 123a freon+oil additive, which equals one pound of freon and check the inside a/c vents, getting cold? If its perfect then you are done, the system may have a very small slow leak and if it only takes a one pound can to fill it once or twice a year you are ok, if it takes more you may want to add a second pound can of freon 134a containing a dye additive that will work its way into the system and show you where the leaks are by exposing a color once it hits the air coming out of the systems defective seals etc.,also they sell a sealer + freon one pound can that can be used to try to fix the leak without having to get too expensive on the repairs.
A car's air conditioning system only hold like 2 3/4 pounds of freon, so in the event you happen to over fill the system a high pressure blow valve usually mounted on the a/c compressor will purge off the excess, but let me warn you they blow off without any warning and can startle you. Always think safety first, wear protective equipment. Work Smart, Work Safe.
Happy Motoring!!!

If the smell is coming from the back of the vehicle then it could be leaking from the return line or the filler hose. I would check the fuel filler hose first since you can probably get at it wihtout dropping the tank. You might be able to get to the return line as well which is a small hose that goes to the tank from the fuel pressure regulator to return unused fuel. If the smell is coming from the front of the vehicle I would inspect all of the fuel lines and the inline fuel filter if you have one installed and verify that none of the hose is damaged and all clamps are tight. Check your injector rail and make sure it is not leaking where it provided fuel to the injectos and check your injectors seat to see if there is any evidence of fuel leakage.

If you can't find any leaks in those locations then you are gonna have to drop the tank and check the pump.

The pump may leaking from a weep hole at the bottom of the pump. If the shaft seal goes bad, the hole allows the anti-freeze to leak out.

Generally the temperature fluctuates due to a leak in the cooling system.

The cooling system operates similar to a pressure cooker, with everything sealed, for each pound of pressure on the system, the engine can increase the temperature above the boiling point by 7 degrees without boiling. This is why when a hose breaks, the temperature gauge generally goes all the way up & you will hear boiling if you open the hood & inspect the area as it occurs.

If you lose a pound (more or less) of pressure, even with antifreeze, due to the pressure the system is under, the temperature will rise.

So, when there is even a pin hole sized leak, a gasket that occasionally leaks, a radiator cap that isn't actually holding the correct pressure-all of these things will cause the pressure to drop & an immediate change in the temperature making it hotter and as it re-seals itself, the temp will decrease again. There are a lot of particles floating through your cooling system and these particles sometimes will plug a leak until pressure pushes it out later.

Generally a leak is iindicated by the temp gauge rising higher than ever before. To resolve this, a pressure test will be necessary unless you replace the radiator cap & find it is no longer fluctuating.

Also, this doesn't have to happen each time you drive. Seals leak when they want to & that's all I can say about that. Usually they will reach a point where they will want to leak all of the time but finding them has to be done while they are in fact leaking.

good luck

Is this a Kerma tune? I have the same thing with my 02'. The reason for the drop at higher rpm's is that the volumetric efficency of the motor decreaces in the higher range and doesn't need AS MUCH boost pressure. This is normal.
BUT if you hear anything that sounds like an extra whistling, bussing or a low groan, and is kinda noticable, then you may have a boost leak.

is the system empty? the common leak on this engine is the AC compressor front shaft seal, the charging port is about center of the firewall on the larger of the two AC lines, the system holds 1.88 (21/4 12 ounce cans) pounds of R134

you have a boostleak, i build gsx's my roommate owns 4g63 power, give me your email er cell and i will send you a boost leak detector you hook up to the turbo inlet and shoot pressurized air into it and if you have a boostleak it will leak out of the engine somewhere that is your leak you replace the seal or hose and blauw the car is fixed, hook me up with blue feedback since im going this far out of my way. the reason you cant get past 2500rpm is because unmeetered air is being let in post maf sensor and the ecu is trying to richen up the engine which is causing the black smoke and probably a strong smell of fuel. my current dsm is the 9th one ive owned =) they break alot lol easy fix though.

hello amit