How do you know if your MAF is bad?
 

I purchased an 87 951 last year. One of the issues I am dealing with is a lopey engine. When you first turn the car on, the engine sounds fine, however after it warms up it starts to lope. Once it drives for awhile it does not lope the same way but the engine doesn't sound smooth. It sounds like the MAF to me. Can anyone point me in the right direction?