Hey Im Fairly new to this site, and to my car for that matter.
I have a 95 Z28 With all the free mods, and a while ago I did the
Maf descreen and Port mod with a hack saw and a basic port and polish kit. I did it fine didnt notice any difference but maybe gas mileage, but could of came from k&n cold air intake which was done at the same time, anyway my uncle did my complete tune up
and he said my maf sensor was backwords could that of hurt car, performance, of maybe ran my car in speed density mode.

 

The MAF is marked as to which side goes toward the air cleaner. It would not have caused you to go into speed density mode. It may have upset the reading just a little because the bars on the MAF are u-shaped and air flow would not have been smooth over them. Not anything serious, IMO.

If you had read more about the descreen and port idea, you might have come across more recent wisdom that says it is better to leave it alone.

 

LOL, so that's the direction the arrow suppose to be pointing?! I wonder how many people were guilty of that at one point.