Will not accelerate. Runs smoothly if you can get

Need to take to a shop with a GM tech 2 or higher scan tool. These tools can actually display various sensor readings and voltages in real time and can be used while driving the car to recreate the issue. These are super expensive scan tools so most shops don't have them. Call around or bite the bullet and have a dealer do it. The money you spend on a correct diagnosis will be saved by not throwing random parts at it based on guess work.

Most cars have a rev limiter built in and will not let the engine goe past 4000 rpm's you may want to change out the spark plugs as often if it has flooded just once the plugs do foul out

IF you have a carby then take it apart and clean it out as all the throats are not working properly including the accelerator pump.

run fault codes and check for accelerator position sensor problem Check for MAP/MAF sensor faults.

You have to change your clutch kit. I just had this issue and after changing it it runs smooth again.
Just to confirm, you shift gear up, your engine roars (goes up to 4000 or more RPM) but doesn't gain speed until few seconds later after the RPM is back to normal.
If so that's the clutch plate causing the issue.
Please rate

I'd say sounds kinda like a missfire although with the absence of an engine code I would lean more towards a vacuum leak somewhere. Chk all your lines while cars running to see if you might have a vacuum leak.

it cutts off the fuel after 4000 rmp check the cutt off switch

Have you checked the fuel pressure regulator for leaks into the intake

yes it could be. have fuel pump pressure tested, fuel pump pressure should be. (key on engine off) 1999 to 2000--with egr--41 to 47 psi without egr--52 to 58 psi,

To do this in park or neutral is normal. To do it while driving is not.
There are so many things that could cause this but if you have no check engine light and it runs normally up until then I would suspect you have an exhaust restriction. This can be checked fairly easy on this vehicle, it has a DPFE sensor that mounts near the top back side of the motor.It will either be black or silver,will have a 3 wire connector to it and 2 hoses going down the back of the motor to the exhaust. You can disconnect one of these hoses and install a vacuum/pressure guage and measure exhaust back pressure. It should be 1 psi or less at idle and when you go to wide open throttle should not exceed 3 to 4 psi. If it does something in exhaust,most likely one of the catalytic convertors is stopped up.