I installed the LTCC kit in my 96 Impala with ACDelco LS1 Coils, Taylor Magnacore wires, and ACDelco plugs (gapped at .050). I even put a new Opti on the engine just to make sure everything was "new." I took the Opti apart before installing and removed the rotor button tab. I didn't remove the entire rotor, just the metal tab on the end. I also loctite'd both screws in optical sensor disc. I started the car and it runs like a beauty. I was very happy with the cleanliness of the install and everything seemed just fine.

HOWEVER, after I took it out for a test drive today, I immediately felt like the engine was sluggish (like back to stock power), but I proceeded to drive. When I got out of my neighborhood, I decided to open it up a little... I floor the throttle and the car took off nicely, but as soon as I hit 4000rpm, the engine backfired and cut off.

It started right back up as if nothing was wrong. I got back to the shop and while sitting still, I revved the engine to right at 4000rpm and the engine backfired louder than I've heard an engine backfire before and cut off. It starts right back up though.

My LTCC kit green light is on with no flashing red light. No check engine light. As I said the engine cranks right up and runs very nicely. I did notice a little more engine vibration when idling though.

I do have a PCM tune that I had PCM4LESS tune for me about 8 years ago. Could that be the issue since I have modified the ignition by eliminated the ICM and factory coil?

Can you give me any input on this issue with my Impala?