I've been having a problem with my 99.5 1.8t. Had a really bad idle, found a few vacuum leaks including a broken line on the N75 valve. Idles pretty good now, still starts up a little jumpy but holds perfectly at about 900 after I drive it for a minute. My problem now is the car will not rev past 4000 rpms. If I am driving it will feel good until about 3500 rpms then it just feels sluggish and it will not rev past 4000rpms. It holds at 4000 like it is the redline. I get a CEL sometimes but it goes on and off. Its P1565 throttle position lower limit not attained. When the code is on my transmission also slips and shifts extremely hard. (Automatic Tranny) If I clear the code the transmission shifts great. Do you think my ECU could be in limp mode and is causing me to not be able to go past 4000rpms? Thanks

 

That's pretty much what is happening. The throttle position sensor isn't in tolerance and the car doesn't trust its outputs enough to let you go WOT. do a search on throttle body adaptation and try that out - see if that helps you out.

 

I've done a throttle body adaptation a few times and it still has the problem. I'm going to take the throttle body off and clean it and hopefully that will solve the problem.