Help with my FC Turbo please!
 

So my stock S5 turbo has been acting retarded lately. My car is having major isues keeping an idle. I need to rev the crap out of it to get it to go but only to get it to sputter around. It revs pretty smooth gradually to around 3-4k rpm and then sputters again and puffs out black smoke. I checked the lines and they seemed okay. I am thinking it's my plugs/wires/fuel pump. There is not oil leaks and the engine isn't smoking too bad. There is not check engine ligiht. My friend said it could be a blown seal. If it was blown would there be a light or some symptom? Thanks guys I def need help here.

bite the bullet and take one plug out from each housing. remove the fuse for the fuel pump and have someone crank the engine over and compare the 2 housings. im betting low compression mine was doing the same thing. elimanate the compression first then check fuel pressure, spark and what not