if your maf is bad do you replace or clean?

You can clean with a q-tip and some sort of cleaner (if you do a search you can find what works best), but you can easily damage it, and cleaning it may or may not fix your problem. I'd give it a try, as it wont hurt. But it may need to be replaced.

Use electrical parts cleaner and a very soft touch with a Qtip. I cleaned mine and the problem kept coming back, but it can extend the life of your MAF until the day you just need a new one.

the reason i asked was because i had gotten into an arguement in another forum. i've been working on cars for 9 years. i never cleaned one and was wondering why people did.

Well there is the belief that it can get dirty from things like over-oiling a K&N filter. When this happens some beileve that the actual MAS sensor can get oil on it which will screw up readings. So some recommend cleaning it if problems arise.
I personally have never done it, but do know some who have with a variety of results.

Yeah, mine was fine for 80,000 miles; clean, shiny, wonderful. Within 3000 miles of adding a K&N (which I'm sure I over oiled) it was coated with junk. It looked like a dryer lint filter practically. It had caught oil, then any tiny particles that made it past the filter. I removed enough junk that it was about 1/4 the size of the head of the Qtip from the inside of the MAF !

I cleaned mine three times and each time it lasted about 3000 miles before throwing another code. I bought a new one and solved the problem by moving the MAF downstream closer to the TB... and by limiting my oiling