Jones Maxflow - Not great?

mufflers sounds different depending on the engine they are behind,the gearratio,converter and where in the exhaust system they are and so on. it is what it is.

Oh yes. This is very true. My combination isn't anything exotic. 4.10 gears, 2600rpm stall, mufflers in stock location.
The one thing that I did which may be relevant is that I just used turn-down pipes after the mufflers and got rid of the pipes that went up and over the axle. This shaved ~25bs off of the car...but could this be the difference between "good" sounding exhaust and the odd "thudding" resonance that I have found? I suppose it could be.

Has anyone else run these mufflers? Were you happy with them? what was your setup?