I got a b16a2 USDM swap in my 96 EK and it had a stock muffler so I took off the muffler and its running headers with no cat to axle back pipe.

Is it normal to be getting some backfire when I let off the gas and its at a mid RPM? It doesn't happen all the time.

I also think what may be causing this is the previous owner had the smart idea to run the motor off a JDM P73 TypeR B18 computer. Im gonna be trading the ecu for a P28 ecu in the next day or so.

 

Backfiring isn't normal. Also check the ignition timing with a timing gun and the service connector jumped. Any CEL codes?

 

The excess fuel from the Type R ECU could maybe cause a backfire. I am not sure of the fuel and ignition maps on the two. Not having an exhaust system could result in burning valves and you're losing power in your mid and low range. Get a full system on, header to muffler. If you could borrow someone's ECU from an EM1 or the 96-97 Del Sol VTEC, that would be ideal. A P28 will not work unless you convert your car to OBD1 or get a conversion harness, and then it would still have to be chipped or run an air fuel controller.

Definitely check your ignition and valve timing out. And if I were you, I'd try to just straight up buy the correct ECU and keep that Type R one, it may come in handy later.

 

Apperently my friend said he has the conversion harness from obd2a to obd1 for the p28 si ecu and it would work fine for my car and he knows quite a bit about hondas.