I have a 91 cavalier 2.2l that I just replaced the head, bolts and gasket..crank position sensor..intake gasket ...and removed the cat converter temporarily...and it still misfires as soon as it reaches operating temp. From a cold start the car runs great, 10 mins later backfire through the TBI. could this be a sensor gone bad? maube the one in the thermostat housing? any help would be greatly appreciated

Thanks
E Britt