[layinrocker65]

If I’m reading the thread right, your using the stock regulator in the stock early year LS truck rails. The regulator for flex fuel is different than the standard(non flex fuel) ones per online info stating the flex fuel runs at a lower pressure. So changing the regulator or rails to a regular(non flex fuel) setup will test if my theory is right. It will(or should) put the fuel pressure to the standard LS 58psi and if the truck runs normal, it’s an issue with the tune.