Quote:

put them in back fired thru throttle body once, and nothing else




The 2.0 Ztech is one of those variable valve timing engines. Perhaps something is up with the VCT mechanism? While the timing belt is off, does the cam gear seem to be "loose" in relationship to the camshaft? Is the cam gear phased correctly in relationship to the crank gear? I'd suspect bad valve timing when you mention "backfire".