manifold vaccum for vaccum advance ?'s

Wow after reading all of this i'm considering just buying brand new cylinder heads...... It kinda sucks, but if i caused alot of damage by running too much advance at idle. The ignition module i am running is just a car quest brand module, its the higher ignition line module not there red boxed garbage.
I was wondering if maybe the ignition module could be at fault for the thudding out the exhaust issue. I have a mopar gold ignition module, but it states that it is to be ruced for racing only... I am thinking tommarrow i will plug in th gold box just long enough to determine if the thudding out the exhaust while at an idle will still continue.
I really hope i didnt do too much damage to my cylinder heads? Like i said it never smokes when first starting it, and while its in oark i can run it up to 4000 rpm and back off the throttle and it doesnt smoke then ether. It will only smoke out the pipes if i am driving it and i'm around 4000 rpm and then back off the throttle?
since it only smokes when (driving) is that a another clue to point towords it being something? Like valve guides or valve seals? I'm going to schedule an appointment to get a compression test and a leak down test.I will then go from there, thats about all i can do at this point, that and change the ecu over, but i doubht thats going to take care of my smoking out the exhaust issue. Thts the one i'm most concerned with right now. Lets say i did mess something up in the cylinder heads like valve guides or valve seals, would i be better of just cutting my losses and buying a new set of cylinder heads? i am really interested in these iron ram cylinder heads. Unless the valve guides and valve seals can be repaired fairly easily? I dont know if it would be a better idea to replace whatever i hurt in my current cylinder heads or if it would be a smarter idea to just get brand new cylinder heads? Since the engine never smokes upon start up thats giving me hope that i didnt hurt the pistons or the piston rings. and its making me think something in the cylinder heads went bad and thats why i'm getting the smoke out the exhaust when i back off of the throtte.
But the leak down test and compression test should answer some questions. Once i get it done i will post the results in the small block section so you guys check them out and then point me in the right direction for the next step i should. Thank you everyone for your responses truely do appriciate you guys's help.