So, it sounds like the Mac works better on a bigger motor. I'll use what I have now (stock head pipe, Ryca muffler) for my not so crazy motor.
Someone had the Mac on closeout on Ebay. Should be here tomorrow.
With shipping and tax, $227!
I'll save it for the 695 top end incarnation.

Great price.  Why don't you try it on your current engine?  Your bike is so light I doubt you will experience any problems with lack of low-end performance.  

I'm not runnin the MAC muffler but the head pipe is workin well on mine.  Its so easy to swap out the exhaust, you could do a cool comparo test.  I would do that on mine, but I can't tolerate the noise.  The MAC muffler is major loud.  

The steup I have pretty much attaches the stock muffler to the MAC header, in shall we say, a semi-permanent fashion.  It's a royal pain in the keester to remove the muffler from the header.  I take it off all in one piece.  But you currently have a stock header set up with a muffler, and the MAC system including a muffler.  Easy swaparoo.  Switch em back & forth a few times and let us know how they compare.  

That really is a great price.

Ug, I hate loud. Might have to make a combo system.

I like loud, but the Mac is beyond obnoxiously loud. My pair have both run a stock header with 12” glasspack and 29” baffled fishtail end pipe. Had to baffle it, just the muffler and end pipe made it sound/shake like an antique Huey helicopter.

Tried the Mac muffler... sounds worse than a straight piped smallblock.