Slant 6 turbo how to set timing please help I will even pay

Sounds like it might be going lean, with the backfiring and hesitation. Accelerator pump maybe?

Is this blow through or draw through? I fought with a holley 390 for years and it was love/hate and it wasn't even boosted. Ran great till it sprung a leak or a gasket shrunk or the vacuum secondary diapraghm tore or it got too hot or the choke failed or the moon was full