Backfires under 10psi plus boost

[cswrench]

Got an 85 with an add on IC conversion. 87 ECM and coilpack/module.
90% of the time at 10-12psi boost it will backfire thru the exhaust. If i disconnect the cam sensor, it will pull to 18psi boost and run hard for 2-3 seconds then the engine shuts off!?? We have tried every known fix with no success. Any wild ideas?
Thanks,
Rob

 

[WhiteT78Supra]

change to new plug wires also ck engine tie down strap

 

[FWD turbo]

change to new plug wires also ck engine tie down strap

Why the tie down strap?

Please explain, as I am having some similar issues right now.

 

[boosted84]

when you converted to the 87 module and coil did you buy the adapter in the harness