i driv my car hard not so long go, an the next day it started runnin like a bag of shit, like it was on 3 cylinders, so i did compression test an there was none in no.3, so i took the engine out an checked pistons they was ok, so changed the stage 3 head for another one off a fiesta using a conversion plate so it runs on mfi still, now engine is fitted an everythin else, wen i try start the car it wont start, i hav good sparks/changed plugs /changed leads/ timed it/ got petrol enterin meterin unit an leaving it an goin 2 injectors, any ideas?