84 is popping/backfiring

My question is what would cause these 351 to pop and crack out of the exhaust like a motorcycle running no baffles?

Some information ahead of time, my truck is a straight pipe exhaust running true duals without cats and dump right in front of the rear tires.  I have not had this popping until now.

So most of you know the starting woes I had with the slow start scenario in the 84.  I have gotten that sorted out and put in the new starter so that is fine.  But at some point I found my distributor was not tightened down and it has been ever so slightly twisted (I do not have any marks between it and the manifold to determine where it was originally).  Once I got the slow start figured out I cranked it back up and noticed its popping and crackling in the exhaust.  It runs fine but just pops and backfires like a badly tuned V twin motorcycle would do.  This was not a problem before and once I found the distributor was loose I can only imagine this is the reason because of timing.  I tried twisting the distributor at about 1/8th turns left and right to see if I could find the sweet spot but no luck there either.  Twisting it too much made it worse one direction, and too much the other direction made the carb spit air/fuel.  I also hooked up a vacuum gauge and found that my motor is running around 17-18 on the vacuum gauge when I get the mixture screws at their peak.  

Is the popping just a timing problem most likely, bad carb mix, or something else going on?  Like I said it has never done this until now, and I noticed the distributor is twisted.....checked that out and found the hold down was loose so I guess it spun between Friday and now.  I have tried moving it (the distributor) as slowly as possible in both a clockwise and counter-clockwise direction while the motor is running to see if I can get it to quit, but no such luck yet.

What have I done since it was running right?
-New Starter
-New Starter relay
-New Voltage Regulator
-Found the distributor twisted clockwise more than before (based on location of the vacuum port, it use to be somewhat straight forward, but now its twisted left).

I bet I goofed up the firing order on cylinders 2 and 3 now that I think about it.  I had disconnected the plug wires to make room for my socket/extension under the exhaust header when pulling the old starter and putting in the new one....I bet I wrongly connected them back up.....in fact I am guessing that is probably what happened....if so I will just put my dunce hat on for a while.  More to come tomorrow.

Boy, that would do it.  Hope that's it as that's an easy fix.

well update....not really a good one either.  I checked the plugs to make sure they were right and the firing order is out of whack based on the distributor cap.  Disclaimer I have not messed with it since I bought it so I dont know how this thing was even running to begin with. 1 8 4 5 and 6 were correct but instead of it finishing off with 2 7 3....it was 7 3 2.  So I am just resetting timing all together now.  Could explain the running issues I have been having since day 1....but again I dont know how the hell it was even running anywhere close to right.

That would cause weird problems.  Hope you get it sorted, quickly.

Ferninand was having problems with the firing order because a different cam was installed.

Thought I'd mention that.