94 c220 hard starting/ shuts off at low rpm Please HELP
 

Hello everyone, i have a 94 c220 with 125K
had the car for about 4 month's without any major repair expenses, then one morning right after i installed my body kit, i found that the car wont idle, if it will i have to keep the foot on the pedal or adjust the throttle stop to keep it at 1500 rpm a friend of mine recomended me to a shop wich is 200 mi away, so i took his word for it, took the risk and drove the car there, they had the car for 1 month exactly, the only thing that they found bad was the wiring harness insulation dry rotted and shorted the TPS and the idle speed actuator wires, replaced the wiring harnes and the actuator/tps 1300$, the problem is still there, i drove the car back the way it is and now will try to find another shop, it seem as the car is in "limp" mode i was thinking it might be the computer, but wouldnt it emitt a code when you scan the ecu? If anyone know's what do i need to do, or where to start. I wish MB would give out more info as far as electical schematics with testpoint voltages that are supposed to be present, when the car is running. Please help.
thanks