Well in my evo wen my turbo went and it made more of a supercharger sound isnted of a turbo sound. If it makes a loud whiny sound then its most likeley one or both of ur turbos are gone. Thats my 2 cent plz correct me if im wrong.

 

Pull of the valve and do the test outlined in this pdf:
http://www.forgemotorsport.com/media/valve_service(1).pdf

 

There are 2 limps modes on the S4, one is for the engine, & the other is for the TIP trans.

The engine one, cuts boost to 5psi, and cuts timing. It will be dog slow. There is usually a big boost leak, or a bad sensor, that cause it, basically something need to be so far out of spec that the ECU can not compensate for it & throws limp mode.

Same for the trans, but you only get 4th gear, yes, even at a dead stop you only get 4th, it slips the TC a lot. Usually the gauge cluster will be blacked out where the PDR5432 is

 

hissing noise as in a large boost leak?

 

is it a whinning noise or is a bad noise? i have a chips car on ko3's. they have recently started to whinning from around 2 to around 3.5 thousands rpms. heres a video of what they sounded like. sorry for the low sound thats all i could turn it up.

Click here to watch turbo-sounds

 

Usually when a turbo goes out you will hear a loud grinding noise caused by the impellers making contact with the turbo housing.

 

did you find out what was wrong? i have the same problem. i was taking an aggressive turn and hit a bump. after that i significant power and have a hissing noise as if there is a boost leak. my check engine light also came on. i don't have the div valves and bipipe, so i'm ordering that now.

 

yeah lke they said up there it sounds like a boost leak. i would check the tbb first then near the intercoolers or jsut save your self some time and get it all pressure tested. or be like me and order an new samco hose kit and wont have that problem any more.

 

i ordered the samco ttb, f hose, and div valves. you think it's worth it to order the complete samco hose kit?

 

idk .... i think it was worth it i also replaced my tbb with a bipipe but that is a later up grade. you have to think about how old your car is mine is seven years almost eight hoses just dry out and crack. also check the vac hoses near the dv's some times they come loose and crack too. i look at changing the hoses like your t belt, one of the last things to chage you forget about but very important.