I would recommend plugs, wires, high flow air filter(k&n, spectre, etc.)supercharger oil, supercharger coupler if its still stock, and engine oil.
126 unless you get a tune then it could be more
A Grand Prix can idle rough for many reasons. The timing may be off, the fuel filter may be clogged, or it may need a tune up.
Give it a tune up. Change the spark plugs and wires..
Austrian National Anthem
what cause a grand prix to not have a lot of power going up a hill or free way? It may be in need of a tune up including air and fuel filters.
Planet Funk - Chase the Sun
stock can go up to 126 but with a tune and some mods, even faster.
I have the same problem and I was told, by the dealer, that the fuel pump module isn't holding the correct pressure after a "warm soak" and needs to be replaced to the tune of $1,000.
needs a tune-up and possible carburetor work.
No actural problem with transmission after 130K miles on a 97 Grand Prix GT, but problems with a ability to get transmission in gear. Turned out to be a bad relay device in area of shifter system in tune with the key interlock system.
Replace spark plugs and wires Replace fuel and air filters Replace PCV valve
were the plug wires replaced in the right order or did they get mixed up? were the new plugs properly gapped before being installed? if you didn't use new plug wires, maybe a broken plug wire? make sure the plug wires snapped onto the head of the plug securley what all was changed out when you had the tune up done?