Running rich?

94 GT stcok except K&N air filter
174,000 miles
Runs rough one day and just fine the next day. Intermitnat problem. Engine shakes like hell.

Changed:
fuel filter
spark plug wires
plugs
cap
rotor
PCV valve
cleaned MAF
Ran injector cleaner directly thru fuel rail (car ran 80% better for 40 miles)
pulled and cleaned injectors
replaced one injector I thought might be bad.
car ran great after injectors pulled and cleaned for one day, then problem returned.
ran about 5 bottles of gas dry thru a few tanks of gas
ran injector cleaner thru a few tanks of gas
Code scanner hooked up and did not show any codes. did show the engine running rich on bank 1 of fuel injectors (passenger side)
code scanner readings showed timing off, but that is thought be caused by the engine running rich?
harmonic balancer appears good.
Car was running rough one day and as I drove it I turned the engine off and then back on about 5 times and the engine settled down for about 40 miles.

Any ideas?

Thanks!

I am at that point where it is easy to start throwing money around to replace fuel pump, fuel regulator, MAF, IAT, EGR, EEC, O2 sensors. I don't have the $ to do all that and I am looking to see if anyone knows of any other diagnostics that would help narrow the problem down.

Thanks

I think I got it

I got a lead on a good mechanic. Within 15 minutes he had it narrowed down to a bad harmonic balancer. Putting one on tomorrow. I'll let you know how I make out. The mechanic did say that I would have done some serious damage if I kep driving the car with the way the engine was shaking. I think I may have gotten lucky.