I haven't had time to do more detailed diagnostics.
I just got the truck 3 weeks ago.
Wihtin the next couple of weeks I'll try to diagnose the backfire. If the accel pump is worn, I'll probably put a kit in it. I may find some goop the idle circuit that is contributing to the other oddity.

I'm using the stock intake manifold.
It has a single 1/2" IPT hole in the side for the wipers.
I used a bushing to reduce it to 3/8 IPT, then an elbow to connect it to the 3/8" hose.

What size does your setup use?

regards,
Leon