98 Beetle rough idle after 20 seconds

On initial start my 98 Beetle idles and runs fine for the first 20 seconds and then it idles rough and misses on acceleration. It seems like water in the fuel but I've put 2 cans of "dry gas" in and why does it run normal at first? Any clues are greatly appreciated.
I checked at NAPA for a MAF sensor and they want $90.00 so I hate to just guess.

Also, there is no engine light on. ??

a new vw one is about 60$

Okay, Thank you. Do you think that based on the problem described that it could be the MAF sensor?

a new vw one is about 60$

wow, where do you get new MAF for $60 at?
I could really use one!

My 2000 beetle 1.8L Turbo is idling super low. I cant figure out how to raise the idle