i bought a 2002 s4 last month with 120,000 miles on it. has full neuspeed exhaust, mtm tuned ecu, darintake mod. i installed boost guage to see what psi this car was running at. after installing it i noticed it was hiting 19-21 psi and then tapering to around 17-18 by redline. that seamed very high to me since mtm suppost to be a lower boost tune i thought. anyways, i got on the freeway yesterday and noticed its only pushing around 15 psi now and taping to 11 by redline. it isnt smoking at all even if i sit there and rev it alot, and it is pretty quiet as far as whistling goes. it does have a lil whistle but nothing more that when i bought it and i think its just the darintake hole. sound like a blown turbo?? or boost leak?? or the factory dv's went bad??? how do i check this out and know what to replace??? thanks guys

 

I would first replace the dv. If they are not Audi TT 710N diverter valves replace them anyway. When do you hear the whistle? At WOT or when the turbo are just spooling up?

I too have the MTM ecu. I've notice the it to peak around 18-19 psi and other times it peak but hold at 15psi. Seems to vary on what gear and what rpm I'm at when I go WOT. If it won't hold around 15 then something is likely wrong.

I would first consider doing some basic maintenance then going off replacing the turbos... If the engine is not getting enough fuel the boost won't be as high. Consider changing the fuel filter. Also change the sparkplugs, air filter and make sure you are using premium 91 or higher octane fuel. And it does hurt to get it scaned to see if you have any codes

 

^^^+1^^^ Plus weather plays a roll when its cooler outside a can see about 2 psi extra and hot days i can lose up too 3 psi depends on how hot the car is too....

 

i just had audi do a 120,000 service on it. they did plugs, filters, timing belt, fluids, waterpump, etc. so i know the routine maintenance is good. it was driving great when i got it back from them. it is making the noise when the turbos start to spool up. also when i rev it i can hear a whistle noise. guess i will give those 710n's a try and c if the help. it was holding 18 psi easy. now the weather is colder hear and still cant hold 15 barely!! thanks for helping