Car:
1998 A4 Quatro 1.8T - 115k miles - Manual - No Mods

Problem:
Car is very slow, loss of power, feels like valet mode. A month ago I replaced all the coil packs and O2 censor and still had blinking misfire error. Yesterday I replaced the Ignition Control Module and the error went away.

Now I have no power. It feels like the turbo doesn't engage and the engine is louder than usual (nothing crazy just louder). It took me 15-20 seconds to get to 35/40 mph. Before the problem, I would be in first gear at 3000rmps, floor it, the car would pull hard. Now it wont even come close to that.

Is it catalytic converter? Turbo problem? Some sort of line?

 

could be stuck in limp mode because of the misfire problem. unplug the battery for a few minutes and try again.

 

You shouldn't be pushing the car hard when it's at limp mode. Pull out the codes and post them up.

 

Also check your maf....
I had the exact same problem and it was the maf...
Try cleaning it first with some crc and if that don't work then you probably need a new one....

But yea first things first pull the codes it could be something else

 

There are no codes. I disconnected the batery and it didn't change. How do I check MAF?

 

do you have a vagcom?

 

With a vagcom
Or if u have a friend closeby with the same car..swap em and see if your car runs better....

 

look for cracks or disconnected hoses i.e. the wierd threadlike hoses especially. they literally flake to pieces

 

Took it to my mechanic and he figured it out! It is the catalytic converter. Because of the misfires it melted the inside of the cat. Basically the engine is being choked because of the clogged cat.

So for future reference... Misfires if not dealt with immediately (coil packs and ignition control module replacement) lead to getting a new cat.

I appreciate everyone's input. Thank you guys!