I just went through this.
I removed the injectors,
clamped a hose to nozzle end of the injector,
filled the hose with carb cleaner,
put 40psi of air pressure on the hose,
cycled the injector with a 9v battery.
Flipped the hose on to the normal end, and
did it all over again. Be careful. Big fire hazzard.
It didn't improve my 4000+rpm miss.
That turned out to be the knock detector working.
I installed a 180 degree thermostat with drilled burp hole to get rid of the knock which it seems to have done.
I suspect this was either a pre-existing condition (motor rebuild upon purchase due to melted #6 piston) or may be related to porting having opened up the breathing in the upper rpm range?
Stock exhaust on it for the moment and indications of high backpressure. Getting 2¼" dual to 3" single muffler system installed next week. Works pretty good at the moment, especially in the 2500 to 4500 range. The porting seems to have softened the under 2500rpm torque. Boost was 15psi max before engine destruction (at dealership) and is now more like 10-12psi max but power is up in the 2500-4500 range and it revs freely beyond this were it used to fall flat.
Any suggestions?
Steve Best
94 SC 5spd, rebuilt engine.
Planed, ported, matched & unshrouded heads,
Ported & matched intake, blowercase, plenum and exhaust manifolds.
180 degree drilled thermostat.
Stock air filter, K&N doesn't filter well enough for me.
Stock blower top (cleaned up) and stock exhaust (for now)