I tried installing aftermarket tips today. I sprayed both bolts w/ WD40, then attempted to loosen each bolt. Well, I loosened each one just a tad, and then the bolt heads broke off.
I don't have a power drill (just a power screwdriver), so I don't think I can extract the bolts. I tried sticking needle-nose pliers in through the back of the exhaust tip to see if I could loosen the bolt, but not enough grip/leverage. I might just end up returning the aftermarket tips and stick w/ the factory ones.