I HAVE A MK2 MR2 WITH A BIG END BEARING NOISE,I HAVE BEEN TOLD ITS A SIMPLE REPAIR, AND CAN BE DONE WITHOUT INVOLVING ENGINE REMOVAL, CAN ANYONE CONFIRM?

loud noise under acceleration indicates a failed big end bearing or main bearing
have a oil pressure check done
remove the injector for that piston and if it stops the noise then consider a replacement engine.

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1991 Toyota MR2 Workshop Service Repair Manual pdf download

could be a big end or main bearing but there are a few simple checks that can be done first
1--have the oil pressure checked using a mechanical gauge
if there is a bad bearing there will be low pressure at idle
2 --check the exhaust for smoke under load
if there is a bad bearing , the escaping oil will overload the oil ring and produce smoke
( if smoke comes after idling at lights and on taking off that is valve stem seals)
3--- run the fault codes and check for knock sensor problems
the noise could be detonation under load from lean fuel mixture or incorrect timing
4---check the ignition timing
5-- run the engine when it is knocking and remove a plug wire and see if the knocking stops
bearings will stop knocking if there is no combustion to place load on the crankshaft
That will also indicate which big end you have to check if you have to pull the sump
Too far advanced will cause the pistons to slap the cylinder walls hard for too far advanced ignition
you statement that the noise goes after 40 indicates that it is not a bearing as the high the rpm the louder the noise
taking the foot off the pedal indicates detonation
lastly if all the checks prove good , you could always have the sump removed and check each big end and main individually for damage
sometimes a failing cam chain if fitted ( no motor identified) will knock as the chain hits the timing cover

Google "Helms", they are the largest replacement manual sellers in the country.

Typcially tie rods will only make a clunking noise or a squeak. The whirring sound if would suspect to be a wheel bearing. When you drive, slowly turn from left to right, if the pitch changes than its the bearing.

The lower end of your motor that has the knocking noise will sound like a deep penatrating thud. That will be the rear bearing for the crack shaft. You can find a cheaper place to have it repaired. $3,500 sounds more right to repair at most places

Four things can give you a knocking noise. 1. failed rod bearing 2.failed main bearing 3. Bad piston wristpin 4. broken flex plate (auto trans)
If It's a bearing, likely you are seeing lower than normal oil pressure. Any bearing repair requires the pan to be dropped but to do the job correctly requires engine removal, crank re-grinding or replacement and oiling system cleanout (expensive). Wristpin (piston/rod assembly) can be serviced without engine removal but pan and cylinder head need to be removed. Flex plate is pretty much a trans remove and replace, with new wheel.
Only a good experienced tech can differentiate between the noises so I suggest you seek aid in your diagnosis, though, if either bearing or piston is the problem I'd likely find another engine before considering the repair.

as for the 93 model i would say if the oil pump isn't working properly chances are that the crank and con rod bearings will be damaged and possibly piston i'm not sure about repairers where you are but if i were to pay $1200 i would expect the motor to be rebuilt too if it has done some serious damage i woul suggest a reconditioned engine you should be able to pick one up for around $1500-$2000 and most of them come with 2 yr warranty firstly id check the oil filter and see wether there are any debris in it such as metal or brass filings as for the 98 model with oil pressure light flickering on and bad engine knock i would think it was either a small end bearing or a big end bearing probably best not to drive it to long with a bad knock because a worn out big end bearing can end up letting the con rod come loose and break or bend causing serious damage ask your mechanic to check the engine oil pressure with a guage and put a new oil filter on it (Could be blocked)

Here is what is going on. When you push in the clutch pedal you remove the connection between the engine and the transmission. At this time all the parts in the transmission stop rotating.Since the only parts in the transmission that can rotate without moving the car are the input parts we can safely assume that the noise can only be from there.This can be a transmission input bearing. Worn Synchro mechanism (allows the transmission to shift without grinding the gears)Low fluid in the tranny. Or a bad clutch component. Top off or change the fluid. If it still makes the noise you need to take it to a tranny shop.

it does sound like a big end bearing and yes the piston will come outta the bloc k eventually if you keep driving
it can be replaced no need for a new engine
you will need a engine if it does come outta the side
but to fix a big end is not that much, if u need a new engine for your veichle is about a few grand

but 100 percent big end bearing i done one last week on a suburu wrx imprezza turb all up it was 550 or so