They are "T" tire rating which means that the tire is only good up to about 118. Most likely your governor is about 115. It's sad that Pontiac would skimp by putting $99 tires on a $28,000 vehicle.there good year eagle ls2 tires stock from the factory
You know you could get a tune that would take out that pesky governor right? Contact Chris at whiteautoandmedia.com or something to that effect. He has the only proven way to get rid of the governor and improve shifting along with other goodies.Somewhere between 115 and 120 for me. I hit this all of the time normally in 5th gear. Wish I could go faster because it sounds like the engine wants more.