Does a Bad O2 /EGT cause RPM not to go over 4000

1999 A4 1.8t Auto - Does a Bad O2 /EGT cause RPM not to go over 4000?

stupid question but does a 1.8T have  EGT where is it located? diagram?

I read EGT can leave the Wastegate open causing no boost after certain RPM's

I have replaced Coils/ Plugs / ICM/ MAF/ checked for leaks ...also No codes

no codes or jsut no cel? you might have a code stored. it sort of sounds like you're in limp mode.

no codes...no cel.. checked them again?? how do you reset limp mode

I did reset the ECU..actually put another one in...but still the same

Only the 2.7T has EGT sensors, you can re-set limp mode just be erasing the faults. But something is causing you to go into limp mode.
Is this an automatic?

yes Auto... but its changing through all gears... does a bad O2 cause this ?

Still check the fault memory in the gearbox and brake electronics. A faulty brake light switch can cause this, so could a faulty TR (transmission range) switch.
A bad O2 sensor would most likely throw a fault code.

I dont have VAG can I try it with something else...? take the battery off? im sure thre are no brake light off

where is transmission range switch? also the location of transmission ecu

You need a VAG COM to test these systems.
The TR switch is the entire circuit board under the shifter assembly. The brake light switch does a lot more than just turn on the brake lights.

but does that mean it wont shift properly from 1-5 gear or not go over certain RPm's ....because it shifts fine

To put it short there are several types of limp mode, transmission limp mode will usually limit you to certain gears and illuminate the shift lights all red. Other transmission limp modes can activate the engine limp mode which limits your boost levels and RPM output to prevent damage.
The brake light switch sends signals to the trans, engine, ABS, and instrument cluster, which can put your car in a limp mode.
A VAG COM is a necessity for this kind of diagnosis.

EGT= exhaust gas temperatures. If you're trying to find them look in the exhaust, but be careful they are pretty hot.

this is driving me crazy... still same i changed the ECU and plugs...... what else to look?