type 44 cis troubleshooting ... im stumped...

[Beatty, Robert]

Patient is an 89 early model (MC-1) us spec 200 tq sedan, its chipped but I
haven't verified if its QLCC or one of the tuners chips.  Its not the
resistor/zener mod.  It also has a bypass valve.

Problems are bucking and afterfiring at all rpm ranges.  When problem 1st
occurred I did some looking around and found a leak at the throttle body
which I had replaced previously.  I corrected the leak with a new gasket.
The bucking actually caused the downpipe to crack because the main exhaust
system mount was broken.  I rebuilt the mount and swapped out the downpipe.
In the process, I cleaned out the air filter chamber and the air metering
plate of dirt and other accumulated crap.  I accidentally cracked off the
vacum fitting to the deceleration valve, and since I didn't have another
handy, I simply plugged its port in the U-shaped boot on top of the air
meter plate and removed its vacuum control line from the layout.  I also
found the bucking had torn the elbow from the turbo to the metal pipe coming
from air cleaner assembly.  I replaced this as well.  Verified integrity of
all of the hoses in the intake path with the exception of the IC itself.  

No codes in ECU either.

So now at all RPM ranges and under load or not, the car bucks and spits fire
(which if intentional would be cool, but its not.. heh).  I tried changing
out the distributor cap/plug wires and all 5 plugs hoping that was it since
its acting KIND of similar to bad wires when wet.  No difference.  Looking
through the manual in the troublshooting, it suggests various fuel pressure
problems causing this type of scenario and since I dont have anything to
measure fuel pressure with, I haven't really gone down that path yet.  So
currently I'm stumped.  I was thinking of changing fuel filter, fuel
distributor and anything else I had spares of in a vain "shotgun" attempted
at troubleshooting, but I would prefer to narrow things down if I could.

Briefly looked over SMJ's site, didn't see much that I didn't already know
or try.

Anyone got any ideas?

Thanks!

Rob