Frnichols

I was geting several trouble codes in my LS1 conversion in a 72 grand Prix. Got codes on high idle, running rich on both sides, and the Injector Control Circuit Intermittent - P0507, P0171, P0175, P1222. I replaced the IAC and MAF sensors, checked the connections, checked the plugs, reprogrammed to performance with a Hypertech programmer. DTC's came back. The fuel pressure was on spec at 58-60 psi at the rail. Have 255 GPH intank fuel pump with the return line at the rail. It's a new 98 Corvette engine. It never ran poorly and a Holley rick/lean indicator never showed a rich condition.

Spoke with a friend who's a Buick Grand National expert. He observed that my fuel pressure regulator vacuum hose was conneced between the TB and the MAF. He suggested I connect the vacuum line behind the TB to the manifold. I figured it was worth a try and it worked. It lowered the fuel pressure to 50 psi at idle and I haven't had a DTC since. Engine seems to have better response and overall performance. So, for what it's worth...