My 1991 Isuzu Rodeo 3.1 V6 slowly began to develop an idle issue. At this point it idles fine at start but after moving the idle goes up past 2500 RPM. I can reset the ignition and get it to chill out at a red light but as soon as I move its off again. Throttle body gasket, plugs and wires, TPS, Idle Air Control, MAP sensor, and any hose even close to leaking have all been replaced and ive even taken it into 2 different shops with no results! I am now down to EGR and the injectors in the TBI unit. How can I check the injectors and EGR before paying hundreads of dollars to replace them?