...... So I started to turn the throttle stop screw in, I got it to idle for a very short amount of time before cutting out. So I kept adjusting the throttle stop screw in, it did slightly improve, then I ran out of adjustment. Adjusting the throttle stop screw in, is of course leaning the mixture out, by letting in more air. So I am going to fit the 30 pilot, and try again, when the engine has cooled.
Ya know, you've got to start keeping your terms straight. It can be very confusing at times to know what you're doing.
The Throttle Stop Screw doesn't lean out or rich up anything. The throttle stop screw only adjusts idle Speed up or down. It doesn't change mixture.
The mixture screw (or air bleed screw if you want to call it that) is what changes the air/fuel mixture.
And you say above "adjusting the throttle stop screw in is, of course, leaning the mixture out, by letting in more air".
Now if by throttle stop screw above you mean mixture screw, that's wrong. Screwing the mixture screw in reduces the amount of air thereby richening the mixture.
You're getting backfiring on deceleration and other indicators of lean and others have suggested an air leak at the manifold (and I think your shop suggested an air leak) and yet you seem reluctant to chase that. Put a new manifold on the damn thing and seal it. And nobody in the world runs a TM 32 with a 45 pilot in an Enfield.
And you can't run an unsupported carb. That alone may contribute to a manifold crack. You've got to start back at square one, I think, and do it all step by horrendous step. It took me practically a whole riding season to first learn and then dial in my TM 32 (and other associated glitches) step by tedious step, when I first put it on. It's a bitch, but that's whatcha gotta do.