H2 cuts off when I shift into gear

Could it be a o2 sensor?

no.

there is a "diagnostic" plug not three feet from the ignition switch...this will tell you any troubles for failed items...however would NOT identify a bad fuel regulator...as this one could have a torn diaprhagm or vacuum hose fallen off...would create this condition and not be detected by the OBD-II~ check your fuel pump regulator~

I read it I could need to replace my ignition switch, which has been a little sticky lately. Its a 30 dollar part.. is this bad advice

I meant "pressure regulator" not Pump regulator here is what it looks like~

your car needs to start...will shop~....yeah, some money...but ya gotta if is like you say it is~

My truck will crank, stay started for ever.. but when I put it in gear it cuts off.

Could be the throttle control not kicking up when you put it in gear. This truck has a drive-by-wire (No mechanical cable) throttle. See the following link. Also shows how to clean one, but it might be too late for that? http://easyautodiagnostics.com/gm_electronic_throttle_cleaning/throttle_body_cleaning_1.php

Gonna try it out in the morning. ..to be continued

I tried a injection cleaner let the truck run 4 about 30 minutes. About 12 hours later gave it a boost then drove 20 miles without a cut off. So far so good. Tomorrow new battery then I will see if it actually worked.