I'm sorry for the constant posts in here but i'm gettin nowhere with this car so giving it one more try in here then i'm thinkin of breakin it:

its a 1992 j plate 4x4 cossie with green top engine, full stainless and prev owner advised it had been chipped (stage 1) - one day it just refused to start and a friend of mine who is good with cossie thought it was electrical, i replaced all engine bay sensors with new ones from matt lewis motorsport, ignition amp and wiring has been replaced for new ones, fuel pump and filter been replaced with new ones, new plugs and leads, dizzy cap and rotary arm replaced also. After all this was replaced the car started and ran perfect, best its ever ran! then a couple days later it started missing and was like it was blowing out the spark higher up the revs. after it did that it would start and run great till it blew out the spark again. its gotten worse and now it barely starts and when you try and rev it, she coughs and die and backfires!! any ideas?