I'm just guessing here but maybe you need to check that your EGR valve isn't stuck.

well I got a mirror and checked the crank pulley for missing bolts and all were present, so I decided to put a wrench on the large main bolt and it seemed to be alittle loose. I tightened it as best I could (truck just moves when I turn it hard). I have to set timing again right?

Tightening the big nut doesn't change the timing, BUT
the loose nut could have the key or the keyway messed
up, and that will mess with valve timing and ignition, to
be sure you might have to take the front of the engine
apart and check the valve timing, and as long as you are
in that far you might as well remove the crank sprocket
and make sure the key or keyway isn't jacked up

I think....

     You've got a couple things happening.
- Digger is right you must have some kind of hole in the exhaust letting air in
- You mixture is too rich

The ba ba ba when you decelerate is from removing the restrictions from the exhaust.

When it does the big ker f_____ing bang, thats from rich mixture building up in the exhaust until it ignites.

Example...my delivery truck at work runs like a top. But when it's real cold (-4C) and the choke is full on, before it warms up, if you run her hard and then decelerate it almost gets to a stop and ker f____ing bang. If I wasn't busy I would reset the choke and the problem would go away...but I haven't had time.

     Check your O2 sensor and other items relating to mixture.

Zag

i say stick with the back firing.... it adds character!! lol

Dunno if its the same with cars, but im sure some said to me when my trials bike was back firing that its something to do with the timing.  ?? 

thank you guyz for all the help, you guyz rock. I have been driving the truck around and it seems to be doing well (it does add character though)

what degree advance do you guyz prefer? stick with the 8 deg advance or do you guyz prefer something else?

I move mine around depeding on what i'm doing,emty 10 deg,  towing say 5 deg,large tires 5 deg, bad gas they sell now a days 5 deg with about eighty cents worth of diesel added to it per full tank to help with the pinging, just advance it till it starts to ping and then back it off till it quits pinging and leave it, if i'm gunna b lugging mine way down on a snow run I might run 2 deg advance.