if a motor runs its best the leaner the air to fuel ratio can be set without hurting or spark knocking then what would be the reason of having to change the tune if plugs look ok and its not spark knocking after putting long tubes with a cat pipe (kooks) on it?i know it should probably be dynoed and checked but till i can get it done i wouldnt think it would hurt to drive it til i can get it done.what do you think,retune first or drive it if everything seems ok?

 

As long as you are naturally aspirated it shouldn't be a big issue. A dyno session will give you peace of mind and perhaps increased performance from the long tubes. Your computer may be pulling timing to avoid detonation thereby decreasing your performance. Only your tuner knows for sure! If it were my car I'd take it easy until I put it on the dyno or datalogged it. We had to add fuel to mine after I installed my Kooks/catted X. 3% more fuel to be exact. It was a little on the lean side.

 

After installing my JBA's(no cats) I was quite abit leaner. 13.8-14.0.

 

Doug recommends that he mod your tune after LT's. He modded mine (don't know how much) after the install.

Untill you get your dyno, I agree about taking it easy.....but it will be HARD to do!