B&M Converter is bad

How did it run at idle before they monkeyed with the timing? Did it idle like a POS? Need to run at 1200 rpm? If not you should be able to deduce where the problem lies.

I use an ages old inductive timing light that doesn't have a dial back on it. Works on everything I've ever hooked it up to.

If that dyno was free that's one thing, if you paid for it, I'd be less than happy. Wish I could do work like that, mess up one end of the way an engine runs, and have people pay me for it. :)