I have a vl cmmodore [rb30]motor in a mazda e2000 it was going good but overheating so I put a new head gasket and timming kit on it but ow it runs likea bag of it misses has no power whenI rev it up high flams from exorst I have replaced main computer, gearbox computer, coil distributer & leads, TPS & I have taken the cat onverter off an still not fixed can you think of any thing that I can try.

When you replaced the head gasket, did you have the head machined and the valves examined? Overheating can warp the aluminum head and damage the valves. Simply installing a new head gasket is not enough. Removing the catalytic converter introduces a host of new problems--I would reinstall it right away. What codes were thrown?