Bought a '94 project to revive. Changed all lines, filters, cleaned injectors, fresh gas. Rode 15 miles and it seized. Swapped out used engine off facebook, fired right up and runs great on stand and initially around yard for like 6 laps and then starts getting boggy. Used engine came with ECU so I swapped that too and it runs the same leading me to believe ECU's are the same / not the problem...I'm stumped. On stand if I run up to high RPMs it starts to pop...lean condition? I appreciate any ideas, thanks.