good news and bad news. the good news is the two heads B18A1 and B18B1 use the same parts. valves, guides, seats, springs, gaskets, etc,...with the exception of the cams. the 1991 B18A1 got a power output of 130 HP@6000 RPMs, and 121 FT. LBs of TQ@5000 RPMs. the 1995 B18B1 got 142 HP@6300 RPMs and 127 FT. LBs of TQ@5200 RPMs. i doubt the extra cam lobe height accounts for 12 HP and 6 FT. LBs of TQ inprovements (+.294mm INTAKE, +.298mm EXHAUST) both engines had the same comressiuon ratio of 9.2 : 1 but the bores and strokes of the blocks were very slightly different. the B18A1 had a bore of 3.189 in. and a stroke of 3.504 in. while the B18B1 had a bore of 3.19 in. and a stroke of 3.50 in. other thinges such as intakes and throttle bodies or fuel pressures could have added to the spec gains on the B1 engine over the A1. or maybe the two engines were tested at different locations and altitude air pressure contributed to the two different specs. also the consider is ambeint air temperature, humidity, and were the two dynos the same dyno and dyno operator/tester? the bad news was the master machinest was sick today and i dont feel like callin him at home. i was hoping he could shed more light on this subject