2008 2AZ-FE rougher, throatier idle; and growl on heavy accel out of sharp turn
 

I have a MT Scion TC.

Key detail on the heavy acceleration out of sharp turn is this usually only happens when I've been engine braking into the turn, and not every time. I'm not certain on the rougher/throatier idle, but I do think it's there.

AFR is fine and so far I'm not throwing any codes.

I have not yet done any engine valve clearance. There is no actual shimming on this engine, just swapping out lifters.

What else could this be? Timing chain? I do drive this car very hard. 130k miles. What kind of shop should I take it to to have look at it?

I can inspect muffler, but don't think I'm going to find any holes. On second though, perhaps one of the connections is a bit loose? Eh, the growl goes away soon as I let off on the throttle, and doesn't return, even if I step on it again immediately.

do you have a CAI (cold air intake)? Check all the connections for the air intake tube. Also when is the last time you replaced your spark plugs? I had denso brand in mine that made it growl and rough idle, replaced them with NGK's and no more issue.. (part 4589, laser iridium). Also when's the last time you cleaned your MAF sensor? Throttle body?