[speeder]

I've heard that you can measure whether a cat is functioning properly by aiming a laser pyrometer at the inlet and exit side of it, there should be a certain temp difference(?) Anyone know about this?

Also, since we have some good technical brains on this thread, are those spray cans they sell to clean your MAF worthwhile? If so, I thought it might not be a bad idea with my high miles, worst case is it does nothing. Do they need cleaning? TIA.