well there ya go.that's your answer.drive it over to Mel and let him test drive it with you.he can tell you if all is good and then you can force it to make the noise and he'll let you know if that's just extreme engine lugging your hearing........which is probably all it is.
really,these engines are not too fussy about timing.you can set it at 8 or anywhere between the ditches from 6-10 BTDC and it will run fine.its just that it will run better under some conditions than others is all.
if you run it at 6 BTDC your going to gain max take off turbo spool quickness but your fuel economy might be a bit lower than it could be around 8.
if you set it at 10 then you might notice some loss in the upper rpms when towing but up this way might yield the best fuel economy and perhaps lower EGT's.
there's really no wrong timing between 6 and 10.it's just personal preference.we all use our trucks differently.
but anywhere @ 8 BTDC +/- 2 = no issues in the way the engine should run as far as knocking and smoking goes.
as a general rule though,the more fuel you introduce,the more towards 6-8 range you want,for engine longevity due to higher cylinder pressure the extra fuel creates and the lack of turbo lag.
iv never personally gained anything in EGT nor fuel economy to warrant running over 8.now if i lived down in Texas or out in Cali where they provide premium high cetane diesel.......things might be different.........but then again with the bull moose.....i probably personally still wouldn't go past 8.