I just got my flowmaster today, excited to get that on and hopefully have a bit better performance and gas mileage! Also i started looking into throttle body spacers..what are really the advantages of one? would it really be worth the money? and if i got that and eventually put on a K&N Air intake system would i have any issues with the intake hitting the hood?

Throttle body spacers are garbage, useless on our motors.

And unless you upgraded your entire exhaust to 2.5" you wont see much HP or MPG at all. Just sound difference.

hmm ok..im doing away with some non-needed exhaust components would that help at all? I got a 2.5" Muffler so im eventually going to redo the whole exhaust system..

Larger diameter TB is better than spacer. I think 62mm is about as big as you can go without too much risk of cracking manifold. Other ways to FREE up existing ponies? Well it all comes down to air-fuel-spark-compression. The first three are easy(er)/cheap(er) than messing with compression. To get better air flow get a more effective intake and exhaust system. To get better fuel delivery try better injectors. As for spark, it starts with the battery goes to high output starter and alt. and continues on to the plugs and wires. Also, try removing AC compressor and running a free spinning pulley. So there's my .02! Good luck!

my did do something, I know everyone wants to argue all day and say how worthless they are but I deffinatley noticed a difference in power but it was mostly above 3000 rpms, and I gained about 2 more mpg I was getting 14 now I get 16 so I know it did something and for $35 you really cant go wrong. just my $.02

how would i go about getting the TB diameter wider?

I just got My First XJ in August so im getting her all tuned up and running to optimal performance!

You wouldn't crack the manifold. You would crack the throttle body.

Dyno sheet for proof or

I don't believe you actually got any gain. I think its the placebo effecs.
Your best bet would be to send it to a member named XJfiles (I think) and have him bore it out.

Or get someone with a lathe to do it...as long as they know what they are doing.

Ok now boreing it out would potentially increase HP torque and such correct? Is this something that you could really notice or just not really worth it with the 4.0?

Sorry for all the questions, its just this is my first jeep and something worth tuning up..I had a 99 S-10 2.2l for five years and never did anything performance wise other than an exhaust (which was a mistake, gotta lot of crap for that, sounded like a ricer...nice idle though)

A bored TB with supporting hardware would indeed be worth it.

Think of it this way. A motor is just an air movement machine. The quicker, easier, and more efficiently you can move air through it the more power you will make.

So any modification to one part is limited in gain by everything down the line.

You can open up your TB so the motor can inhale better, but if it can't suck any more efficiently through the intake manifold, or exhale any easier through the exhaust it wont do much.

Yes a TB spacer is junk. Now if you want performance you are gonna hve to go and do a header back, and while the intake is off may as well clean up the ports, get the TB bored, and get a set of injectors. Now to make sure it runs it's best make sure the O2 sensor is good, cap rotor, wires, plugs, are all in top shape, and chraging system and battery is in order. Other than that, you are gonna hve to open the engine up for any more power.

What kind of power are you wanting? and what is your reason behind needing it?

Thank you, i am also part of the group that say it worked for me. Its a small group.

Then post up the Dyno sheet. Because there have been tests done that prove otherwise...

unless you have dyno sheet proof, not butt dyno proof, then this is in-admissable conclusions

yeah i planned on eventually doing headers back, then this winter putting new spark plugs, wires, etc. just put a new battery in a few weeks ago so I'm good there, and getting a K&N air filter in the spring. As far as the injectors go i run Lucas Fuel injector cleaner a couple times a month to keep then cleaned out..would it really be necessary to change them out?

allsierra - why not have more power :P it just makes everything a bit more fun!