What do you think? Can the rotax 912 get a power bump with a free flowing exhaust system. Most of the existing systems out there are only for quiet. Not for max power. Does anybody have any experience with different exhaust designs for the 912?

Mr. Milless made my new exhaust to custom length for that purpose but we don't have it installed all the way yet to know, plus we will never really know because its apples to oranges with the turbo.
In theory it will give you more HP.
Somewhere in this video he explains it:



https://vimeo.com/78298496

TMI:

Mr. Milless just stopped by on his Cristmas joy run and I have to pull the engine back off to get the oil tank out to modify...and it's 25 degrees in my hangar so it won't be running any time soon (because I'm lazy and stuff).

Greg,
Since you have that engine pulled off I think the best thing you could do is send it up here to the frozen woods of Northern MN. It really should be tested thuroughly in this climate before subjecting it to the hills of Ohio! It is the least I could do for you. I am just looking out for your safety and well being.