swapped my 1500 carb engine to the JDM D15b 3 stage vtec, the installers and i were in agreement that i would use my stock manual tranny, but the engine they installed came from CVT equipped EK, so the engine has auto ecu and intake manifold and head. they were able to install it, no cel codes, but when i took it home, had erratic idling, terrible gas mileage, and vtec seems not to be working. so first, tried to fix the idling, had IACV cleaned, including the TB, it eased up a bit but idling still erratic, but as of this the moment idling goes to 1500 rpm when gas pedal is pressed although when car is moving only. then everytime i switched the A/C rpm drops, then goes to normal idling around 800-900 then from time to time drops again, but no A/C normal idling unless braking as stated earlier.
2nd and 3rd is gas mileage and VTEC, i am thinking they are inter related? but not sure...
there, tried to be detailed as possible. can you help?