Exhaust popping on decel

[CookPerformance]

Hi guys,
I am new to tuning and I think I might have bitten off more than I can chew starting with a gen 4 .... there is a lot to wrap your head around here. Anywho, I have an L76 with a 6L80 from a 2008 Pontiac G8 sitting in a 1938 Buick Special. The 6.0L has a Comp Cams XFI cam no 146-426-11 so 222 int./ 234 exh, 275/287 duration and 113 separation. It has shorty headers, no VVT and no DoD. The 6L80 is bone stock. I got the car running "ok" but now I seam to have hit a wall. I have very loud exhaust popping when you suddenly take your foot off the gas and I seam to have a hard time fine tuning the fuel .... I make progress and then suddenly everything changes (I guess some correction thing kicks in???) Just hoping a more experienced guy can take a look at this and give me some pointers

[5FDP]

Is the exhaust complete?

I notice that your o2 sensors don't really move around alot and that they are showing lean. You also need a wideband o2 sensor to tune this engine.

Raise the idle timing up a tad to 18-20 degrees. Find the under/over speed spark correction table for park and in gear and cut the numbers to +/- 8 degrees instead of 13-15 degrees, it should tame it down while you dial the fueling in. I'd also raise the idle speed to 750-800rpm for now.

Both the MAF and VVE will need adjustments with a wideband to really get that under control and make sure fuel pressure is around 58psi all the time too.