Cars symptoms were stalling at idle, dies on initial acceleration, breaks down under heavy acceleration. Also got check engine light codes 231 & 221 (lean or rich fuel mixture at cruise) I performed the following:
 Checked all vacuum lines, found one bad line on the fuel pressure regulator, replaced the line, no other disconnected or bad lines found - no change
 Checked throttle bellows for cracks or holes, none noted
 Performed a complete tune up - plugs, dist. cap, rotor, air filter, air box thermostat, fuel filter - Ran better - Still hesitated and broke down under heavy acceleration
 Performed throttle body service - Idled better, still had hesitation and break down under heavy acceleration
 Cleaned all electrical connectors in engine compartment and all grounds, applied dielectric grease to all connectors except oxygen sensor - no change
 Cleaned the fuse buss, applied dielectric grease, tightened the fuse clips, replaced all fuses with BUSS glass fuses - no change
 Tested coil - within acceptable range
 Checked RPM sensor (damaged cable) - replaced, no change
 Checked in tank fuel pump (non-operational) - replaced, no change
 Replaced fuel pressure regulator (just a guess) - no change
 Tested Air Mass Meter (megged out within range with digital multimeter, still not convinced it's not bad) - cleaned electrical terminals and reconnected - no change
 Replaced power surge (just a guess) behind battery on left fenderwell - no change
 Replaced main fuel pump, (thought it might be weak from non-functional in-tank pump) bad and expensive guess - no change
 Went to salvage yard and purchased Jetronic ECM and Constant idle ECM, and constant idle motor, tried all three - no change, re-installed originals
 Checked engine vacuum thinking this might indicate a plugged converter, got 20 lbs of vacuum, don't think it's the catalytic converter plugged
 The coolant temp sensor was changed about a year ago, so I don't suspect it
 Replaced the AMM, car now idles well, does not break down under load. Positive change However, can't reset the check engine light
 Tested Oxygen sensor, failed test in the closed loop mode, replaced the oxygen sensor and was able to eliminate the check engine light and clear all codes. Positive change I thought I had it licked. I drove the car, after warming up when I came down to a stop the engine would surge up and down badly.I tighten up the intake manifold bolts and it seemed to improve about 50%. Soooo, like taking two aspirins instead of one, I tightened it up some more, the surge problem is back to where I started. Now after running the car for awhile the surge is gone, I'm assuming the computer compensated for the problem. Now however, if I cut the car off and restart after it sits for a few minutes it hunts for the idle for about 10 seconds then settles out. It does not do this when cold. I thought it might be the fuel pump check valve but it seems to me that would be a problem at cold start. It starts and idles fine when cold.
2. Do any of you think that changing the intake manifold gasket will solve this? Why wouldn't just tightening it fix the problem? Do you think it's even the problem? Any suggestions other than sell it? My wife loves this car, HELP!!!!