Ignition timing issue,bank to bank

Ok,i have a very odd setup,and the problem im having is a bank to bank difference in spark.

My setup is odd to say the least,but i think ive had this problem before i went to a carb.

Run down on my setup.2001 4x4 1/2 408 4l80e.

408 11 to 1 248 254 660 lift 110 lobe center.

It has a vic jr intake with a 950 bg carb on it.Im using the factory map sensor for the load to control spark and tranny tables.

Problem im having is my pass side bank has alot more lead then driver side.
When i log it timing is were ive set it,but i tried a nitrous pull and fuzzed all plugs on pass side,driver side looks PERFECT,the timing mark on the ground strap looked perfect,when i log it,it shows what im telling it to have,28 total on c16 on a 175 shot,very conserative tuneup.Even on the motor it felt a bit wierd but made pretty good power considering my drivetrain loss with 80e and 1ton t case and big tires,unlocked it made 485whp.But does act a bit wierd.

Ok that sthe run down on the setup,any ideas?like i said i think this problem has been there before the carb swap.i would always have wierd bank to bank fuel trims.this has been there since i did a 6.0 swap,then the 408 as a efi and smaller head and cam,then the carb setup.
Ive put new crank sensors in it along with a cam sensor.Im honestly at a stand still.
Thought about changing pcm and tracking the entire wire harness from coil packs to ecu.But if anyone has something let me know.Thanks

Thanks for anything you guys can give me info wise.

Couple thoughts here. Is your exhaust more restrictive on one bank, causing the other to see better airflow and subsequently a denser charge requiring less timing? Are the coils getting the same charge from bank to bank?

Do you run a shop there in Fresno? I'm originally from Caruthers.

exhaust is all mandrel bent 3 inch,xpipe long tubes.Im going to go ahead and rule out the exhaust.
Caruthers ha.My brother owns the napa in caruthers,i worked there for 6 years.Yes i run a shop in fresno.

I thought it might be you Nathan. I was friends with AJ, had a supercharged 95 GMC back in the late 90s and was at Napa weekly. Shoot, I gave your nephew swim lessons at one point.

Figured you had the exhaust covered, but just spitballing ideas here.

was your truck green had a whipple right?

As far as all the basics,ive got them all covered.Its actually not my truck,its my mechanics truck.He does all the installs and custom fab work at the shop,i do all the tuning ect.

Right truck, wrong blower. I had a Vortech on it. I'm running Magnachargers on everything now.

What was your wideband showing while spraying?

a/f is fine.
plugs show plenty of fuel also.

Its pure ignition issue.

I did a maggy tune for justin gunland.5.3 on 8psi makes over 430 whp threw a 80e and a 14bolt 4.88s and 35s.

What type of dyno do you have there? I have quite a few customers in Fresno and Clovis that might be interested in knowing.

dynojet 248
i tune gms and fords.
all carb stuff,we do lots of stuff at the shop.Full machine shop and custom fab aswell.