I seem to recall this being discussed years ago on this board. Something to the effect that the platform was never rated for the load, etc.
I would definitely do some triple checking before I cantilevered a load like that off the back.
Close! The fuel pressure regulator would cause the popping upon acceleration. It sounds like the throttle blades still aren't synced if you're getting surging at idle. Once you get above idle and the butterflies open, it's likely more balanced and that's why it disappeared.
Tom - I understand all this.
The point I'm trying to make is, there's no reason he has to break the gaskets on that motor to run this test. Go adjust the throttle blade opening using the cables at the shifter (or wherever he has the easiest access) instead of the screw on the throttle body.
OK, so why not do this adjustment using the cable and test the entire theory. If it works, great. You can take it apart and adjust the throttle blade with the set screw later.