I had my mechanic add the following a few days ago:
- Throttle body spacer
- Bosch Platinum IR fusion spark plugs
- K&N high performance air filter to replace OE air filter

I haven't checked gas mileage, but notice absolutely no performance improvement. I had expected a minor or at least noticeable improvement.

Used 2006 H3 stock 3.5 with luxury and adventure packages and 48,880 miles.

I was going to change to synthetic oil, but suspect that that would also provide no improvement in MPG or performance???

 

that should actually. just dont remember the source from which i had found that such oils affect performance in a positive manner.
and good mod indeed

 

I doubt you will get anything from the TBS.

 

I use 5w30 castrol syntec full synthetic and I noticed a difference, I also checked the tranmission fluid and added a quarter of a quart of $7 GM approved tranny fluid and it's like a whole new car. 46000 mile on my rig

 

i use sythetic and noticed i dont have to get a oil change every 3k miles.. now i let the computer get to about 20% which is about 5 to 6k miles before changing.