[s-cars] ur-S4 high load misfire

[Dave Forgie]

Cody:  This is a classic symptom of a failed (or failing coil). They
might be fine with the stock ECU and turbo but more boost via a chip or
a larger turbo and a chip (and injectors) will show up the "failure"
(coil weakness) that wasn't apparent with the stock setup.

I second Chris Chambers' suggestion regarding testing via the spark gap
tester. However, I will add that you might want to pull the fuel pump
fuse, No. 17 (drivers end of the dash), so you don't load up the
cylinders with fuel while cranking to test the spark gap.  

Hope it works out.

Dave F.