Stumbling at high boost... advice needed

[Beatty, Robert]

Hi gang...

Having some slight stumbling on my 87 5ktq.  It has been chipped and has the
1.8 bar spring.  I have WDT-7 plugs in it.  Changed the distributor cap and
rotor.  I havent checked the plug wires yet, i need to thou.  What are
possible causes for slight stumbling at high boost/rpm.  I'm thinking a
couple of things... 

Gas - 93 octane is all im buying thou...

Plugs -  They are the correct plugs for the car but not the 15$ apiece
ones...

Wires -  Gotta check them, but when sprayed with water i see NO arcing or
change in idle rpm...

Vacuum Leak - Where could this one be???

The Audi gods just want to keep me busy working on my car instead of doing
anything else in my life :)

any suggestions on what you might think the MOST probable reason for this
is... its not affecting drivabilty for the most part, just kind of annoying