Thought I'd post this and maybe it'll possibly help someone out as well. Sunday, I swapped out the NGK TR55 spark plugs with one heat range colder NGK TR6 plugs in a stock bottom end LS1 C5 Corvette with ported heads, cam, intake, headers, etc, which makes 430whp & 400wtq and has a 10.8:1 compression ratio. TR6 plugs were recommended by Brandon at Fast Motorsports might I add (who previously tuned the car). First, the TR55 plugs I removed were gapped at .055, had approximately 7k miles of use and were inspected closely and looked excellent when removed. With the TR55 plugs the engine made a not loud but noticeable ticking noise (what I always thought was valvetrain noise due to the aggressive Torquer v3 cam & dual springs) and the car surged very little at lower rpm's. With the TR6 plugs gapped at .045, the difference was quite surprising, IMO anyways. The noticeable ticking noise is gone, completely. With the engine running I had to concentrate to hear any ticking from the valvetrain. Sounds very quiet compared to before. And the best part, there is no more bucking at lower rpm's under normal driving. In lower gears (1, 2, 3) I had to get rpm's down near 1k or under to get any bucking out of it. Definitely a $20 well spent.