Originally Posted by 99 Black Bird T/A

Basically there's probably 99 reasons your car is slow but the A/F at 12 to 1 vs 13 to 1 isn't one of them.

Richard Holdener- Tune vs Horsepower

There's not much difference in how much HP an LS engine makes between 12 to 1 AF vs 13 to 1 AF. My 383 LS1 stroker made the same hp at 12.5 AF as 13 to 1 AF,

To lose ~35 hp you'd have to be at ~ 9 or 10 to AF

​​​​​3eIf the timing is off a couple of degrees that can hurt hp far more.

Originally Posted by 1hotroc

Gotcha ok thanks .I have some different parts to change anyway. 42 lb injectors and going to a fast 92 intake. Will then have it retuned . But my point is that based on what I see Im not getting a true reading when probing after the cats for air fuel reading. It’s off a point if not more .

Originally Posted by LilJayV10

unless you check it before the cat you dont actually know that do you?

also, do you know what the actual commanded is?

if it has cats, is COT enabled? If so, has the COT enrichment values been changed to keep it on the rich side but not full retard rich?

I'm guessing the answer to all those questions is, you dont know.

Originally Posted by 1hotroc

I have checked the value before the cat!
I had mentioned it as clear as possible in my first post that when on the dyno, car had a probe that was inserted in the tailpipe (after cats) . Now I also mentioned that I have now installed a wideband in the header collector which is before the cat. Wot on dyno 13:1 . Wot on Wideband 11.6- 12.0. So is power being left on the table ? Probably