Really stupid question
 

How the heck do you keep the stainless exhaust tips clean when there behind the tire. My truck is always clean but a total nightmare to keep the tip clean, between tar and dirt and salt and whatever else is on the road I can't keep up with keeping that thing clean.

Mine is like that too. The sandblasting is the worst, and the most damaging concern. I think the only solution is installing a mud flap to the back of the wheel well.

I use gas to clean mine. every once in a while i run my buffer over it.

IF IT'S STainless steel and you don't mind a brushed look, use a scotch-brite or "greenie pad" to clean it off. Don't use a SOS pad, it'll leave rust marks from the steel in the tiny scratches, but a plastic cleaning pad works great.
My stainless 6" stacks were polished like that and I use the scotchbrite pad to get rid of embedded bugs at the top when necessary. If you like the chrome look of stainless, you're screwed if it's right behind the tire.

Mudflaps don't help much. I got tired of cleaning mine so I sold it and have none now. I always used Mothers Mag and Aluminum polish. It worked great but you do have to apply it twice. You do it once and let it eat into the tar and then use your thumbnail through your rag and the spots will start coming off. Then go over it again and it will look great.