Timing or carb ?

[Jabes1]

Sounds more timing related. Are you using a timing light to adjust your timing? Initial timing for HEIs should be around 15-18 degrees advanced. Warm your truck up, turn the idle mix screws all the way down, hook up a vacuum gauge and adjust them out a quarter turn at a time to achieve the highest vacuum. You want the screws adjusted the same. Idle mixture is just that....idle mixture. I'm thinking if you get the carb and timing adjusted correctly the bog will disappear. I seriously doubt you're under carb'd or lean with a 4bbl on that six.
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[Straight six]

Well I'm not sure why but today I checked my intake bolts they were not tight I turned them about a half turn. Seems like truck is idling fine no backfire through carb or exhaust. How much could the loose bolts effect truck performance ?
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[geezer#99]

Effects it a bunch! Makes a vacuum leak on the intake and the exhaust flanges can suck in air making the exhaust pop a bit.
Did you do any grinding on the stud washers that hold the intake and header flanges on?
On my offy and langdon's headers the flanges were'nt equal (not same height) and I had to grind a bit on the washers so they would sit flat on the flanges. Check yours.

[Straight six]

Yea thanks I made sure they were pretty even. So they just get loose over time engine vibration? What should I do to not have then loosen again?
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[solidaxel]

Might try some Blue Loctite