Hesitating unless perfect shift/check engine light comes on

[TurboAWDKID]

Guys, I have a 1990 TSi AWD 5 speed that I just got a week ago. It ran great up until now. All of a sudden when I started going, it hesitated really bad and the check engine light came on but the RPM's were steady and not bouncing around. Unless I make a perfect shift (recommended by the manual) it hesitates really bad. Sometimes while I am driving it will do this all the way through a gear and sometimes it will stop the bucking and the check engine light will go off and it will run fine. I checked the plugs and cleaned them off and they are fine (BPR6ES plugs). I'm not sure what is wrong with it, any ideas before I take it to the shop?

 

[Ghost1984]

I would start by checking for boost leaks

 

[steve]

I'd start by reading the CEL code and fixing what the ECU thinks is wrong.
From the description my first wild ass guess would be your TPS is bad but reading the code would confim that.

Steve