Ive been chasing a misfire in my 1997 b20b swap in my 90 si, and finally found that if i pull the vac hose from the FPR and plug it, the misfire seems to go away. it's running a pr4 ecu (obd0) and apparently its lean. really misses at wot at higher rpms even with a wide open FPR. I chased all the ignition possibilities and comp tested 180 psi across the board.

anyone ever seen a pr4 cause a lean condition this bad? just the wrong injector pulse width?

i plan to go obd1 with a socketed ecu sometime this year, but what ecu can i buy for now to hold me over until im ready to dump money on a distributor, etc? has to stay obd0 for now.

 

Fixed. It was a plugged injector bucket filter on cylinder 3.