How do I remedy intermittently po171 and po174? on 1998 GMC Jimmy

I have changed MAF and O2 Sensor. Blew cigar smoke into booster hose into intake to area to detect leak. I changed intake and throttle gaskets. This happens noticeably when approaching a half tank or when driving for long period.

by in Tulsa, OK on April 26, 2013
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1 answer 1 comment
ANSWER by , April 26, 2013
did you use smpke mach to correct smoke pressure? could be a small vac leak that effects both banks. poss low fuel pressure or injector issues,most likely fuel pressure issue
COMMENT by , April 27, 2013
I forgot to include, I did go into intake and replaced fuel pressure regulator off spider injector unit. I replaced fuel pump and tuneup. The runs good just occasional rough idle during when car gets hot. I did do a smoke test by following "Scotty Kilmer" instructions off of "YouTube".