Driveability help please. Iron LS6 +cam dies when letting off throttle

[BagD72Chevy]

Background:

4.8 bored out to 3.898 with vette rods and pistons. New 5.3/5.7/6.0 crank and Texas Speed 212/218, .600"/.600", 111 LSA, 110 ICL. Pac 1218 springs, rods, etc. TBSS intake and 102mm throttle body. This is in a Rock Buggy with a TH400 transmission with a tight convertor and NP205 transfer case. It had a stock 5.3 before that I swapped the engine in. It has no brake switch, no vss and is tuned as a Manual transmission. Stock 5.3 ran fine until it wore out.

Issue: VE is good, startup is good, etc. But it dies when you abruptly let off the throttle. Without the VSS throttle cracker will never be active. Can this be fixed with throttle follower, some other table Im not familiar with, or do I need to figure out a way to change the cable VSS to electric?

[5.7ute]

You need to strengthen your idle and give the timing some range to save you from a stall. One way to do this is to drop your base timing at idle to around 15 degrees and increase the idle airflow. This will give the timing a fair bit of room to play with.
FWIW my base idle is 10 degrees but with a lot bigger cam and it idles flawlessly. (I also needed a 1/4 hole in the throttle blade to bring IAC steps into line)

[VEV8]

I have the same approach 5.7 ute.. lower idle time for best map KPA
However im finding the hi octane spark to base spark gap causing bucking in low speed driving carpark / cruise