Fueling & Injection - Open header read fresh air?

I just put an ls1 back in the car with 30lb injectors and mild cam. We kept messing with the tune and the computer keeps trying to add as much fuel as possible. We even put a complete stock tune with 30lb injector tables in but the long term keeps maxing at 25 and the short term goes to add over 40 before I cut the car off. Can the O2s be reading fresh air because its open header?

how far from the end are the sensors? it could be reading some fresh air

Yes... It is why you kill o2s when you run open headers. Put a couple ft of piping on them.

Yes... It is why you kill o2s when you run open headers. Put a couple ft of piping on them.

This ^^^

Plus doesn't adding a couple ft of pipe help the exhaust velocity/scavenging?

This ^^^

Plus doesn't adding a couple ft of pipe help the exhaust velocity/scavenging?

I'm not sure.. I have seen tests back it both ways so I'm torn with that.

Yeah I've seen a few test where a good full exhaust flowed better than open headers back in the day when I was into Honda's but I don't know about open headers vs extenders.

Thanks, I'll try to find some 3'' pipe locally tomorrow and see if it fixes the fueling

That was the issue. Adding a foot of pipe made a huge difference

Glad you fixed the issue..

had a question about this as well but not dicrectly abuot open headers. If i have a leak between the cat and the LT headers, will this cause a fresh air condition as well with the O2 sensors? i have a NOTICABLE leak on my passenger side collector due to a horrible weld job that is failing now after two years on my SS steal headers to aftermarket cats. kinda pissed.
but would this cause irregular running conditions?

It actually recommended (at a minimum) to add 10X the collector diameter in pipe length to avoid the O2s from reading outside air. So for a 3" collector you'll want 30" of pipe.

had a question about this as well but not dicrectly abuot open headers. If i have a leak between the cat and the LT headers, will this cause a fresh air condition as well with the O2 sensors? i have a NOTICABLE leak on my passenger side collector due to a horrible weld job that is failing now after two years on my SS steal headers to aftermarket cats. kinda pissed.
but would this cause irregular running conditions?

If your gas mileage dropped a fair amount, I would say yes. I'd also pull a plug from the driverside and passengerside and compare them, they should look the same, if not thats more proof for you there..

I doubt a leak from a bad weld will let any fresh air in to offset the front O2's