How slow would it be with 25 polb. rims? Are we talking a big decrase in power?
with a 25 poud rim, acceleration will be almost the same as stock (slightly slower).
as i said earlier, the stock gts 16" alloy rim is about 22 pounds. acceleration according to rims is ALL about weight. so if you get a bigger rim that weighs the same, acceleration will stay the same (although traction will be better--a plus).
so, as you can see, getting a rim that is only 3 pounds heavier will increase drivetrain weight by 12 pounds (3 pounds X 4 wheels = 12). not a very big difference, so your car will accelerate only slightly slower.