I posted pics with my mass air meter missing the front screen a couple of weeks a go(97-960). I posted that it helped with a little extra tourqe off the line, when I first did that little experiment, I had a couple of vacuum leaks. I just received yesterday a mass air meter and housing for a 98-960 with 66k miles on the part. Today I had 27.5 miles to the gallon on the car and could not tell any(after 180k drive) difference in power-if anything she had more. I did notice that going from basic sea level to 3000 feet that I lost a pound or two of vacuum being up high,is that normal? Noticed that from my new vacuum gauge.
Any way if your thinking about taking the screen of of the front of the meter, don't do it, Jbowers was right-the Volvo guys did that for a reason-and they probally know better than the rest of us.
Hope that helps
Poolman