Ok i have a 98 civic ex. We just swapped in a 99 B18B. We got it running and i drove it for like a day. Got in it the next day and now its breaking up hard at 3k. Im running the vtec harness which i dont believe hurts because i am running the P75. I'm thinking ignition coil but i need some thoughts on this. Thanks

did you check the plugs maybe?

I have the SAME EXACT setup in the same exact car except I have the PR4 ecu instead of the P75. I've been using the vtec harness for as long as I've had the swap with no problems relating to it. There will be several plugs left over that will just hang there, make absolutely positive you didn't plug any into the wrong spot and a few have the same exact plug designs.

Test the coil/igniter for sure.

Are your plugs, wires, cap & rotor fine???

we put new plugs and wires on it yesterday. I checked the cap its fine. We fixed a fuel leak that i had on the rail side so im thinking that might have something to do with it. It may be starving

YAYAY!! Fixed the problem! It was starving for fuel!