To get an improvement you have to have a good flowing air intake (something WAY better than stock), otherwise you will probably notice a decrease, or no increase at all. With some of the older throttle bodies (98 and older) sometimes no matter what you do it won't help bring the air in better just because of how they are designed...not all the time but sometimes. With a ported throttle body and a very good air intake on the GTP it obviously does just fine without an MAF screen, and the SSEi with a stock air intake w/K&N filter and stock throttle body doesn't seem to do too bad without the screen either, but both of them are newer than 98. Personally, unless you are really into getting every little bit of performance out of your engine as you can, I don't think it'* worth the trouble..a lot of people have had problems with removing them. I would suggest removing it for a week or two, and then putting it back in after the week or two and see if you notice an increase in performance with it back in...if not, take it back out, if so, obviously leave it back in. That is really all I can tell you. Some just have better luck than others.
1990 Maroon Grand Prix STE McLaren 3.1 Intercooled Turbo, 14.695 @ 94.49 on 12psi before cam/heads/etc.
1990 Bright Red Grand Prix McLaren 3.1 Intercooled Turbo, 14.819 @ 92.72, 189whp
1999 Grand Prix GT 9.75:1|K&N|160 tstat|No Ubend/Cat/Res|UD Pulleys|Ported M90/TB/Heads|XPZ|2.55"|Pacesetters|Stage 2 I/C. 12.442 @ 112.78
2000 Blue Bonneville SSEi Supercharged Gutted Airbox|K&N|3.4"|1.9'*|WP Pulley|Custom DHP|180*stat|41932'*|No Cat. 14.681 @ 94.80
2002 Dark Cherry Grand Prix GTP Supercharged & Intercooled
12.084 @ 114.38 w/1.743 60', 315.6whp, Fastest Stock Cam M90 GTP!
NOW XP CAMMED, 340.6whp with XP, stock heads, Gen 3 M90, 11.984 @ 115.84 w/1.750 60'!
Most HP Stock Heads Gen 3 M90 GTP!
2004 Red Monte SS Supercharged K&N|3.4 Pulley|1.9'*|180*stat|41919 plugs|3" dp|No cat/ubend|DHP|Shift Kit. 14.2 @ 98
GOT BOOST??? Friends dont let friends drive stock!