i'm trying to figure out a problem on a multi-port fuel injection system. when first installed [my first attempt at fuel injection], it worked perfectly, and has gone many thousand miles trouble free. what now is going on, is when the car is going down the road at 1800rpm or above, if you let off the gas, the car does not return to idle. it keeps going as if it has the cruise control set. it then stays there until almost stopped, then returns to idle. the first thing checked for was vacuum leaks, but none were found. the car was scanned in real time, and all functions indicated working as they should be, with no fault codes present, and none pending. since this is a conversion and the computer is a reflashed original, it was sent back to the company after several phone calls with them, to have it checked. it passed their checks, and was returned and re-installed. still exhibiting the same symptom. if in park or neutral and stopped, you can rev it till it hits the limiter as many times as you like, and it returns to idle as it should every time. out on the road, however, if you keep it below 1800, it seems to act as it should. above that, it seems to go into a "cruise" mode. applying the brake has no effect because there is no cruise control on this car. i have checked all hoses for cracks, operation of the pvc, iac motor, map sensor, fuel regulator, throttle body, throttle linkage, and a few other sensors, plus disconnecting the brake booster, and have come away scratching my head. now, i'm wondering if it is related to the vehicle speed sensor on the transmission. this is an add on unit that screws to the original speedometer housing, then the cable screws on to it. the engine and transmission mounts have also been very carefully checked as well, and are in perfect condition. where else can i look ? the car, in my opinion, is unsafe as it is now. the conversion kit people have no ideas, so i'm stuck. can anyone help ? a SUPER thanks in advance ! it will probably turn out to be some silly, little stupid thing. again, TIA.