What kinda changes..

What kinda changes can I do to the stock 4.0 in my XJ to boost the power without having to take apart the engine? Keep in mind that Ive never done any real engine work besides plugs, wires, cap, air cleaner, the usual tune up stuff. I looked at a aluminum head on hescosc.com but I dont have $1250 for the head.

What about a K&N FIPK, or a throttle body spacer, or roller rockers? How hard is stuff like that to do?

The K&N FIPK is a snap to Install, and actually produced noticable results. The intake tube clears the hood by two or three hairs, so I don't see a throttle body spacer fitting. IMHO anyway. Besides that I'm trying to stay away from the snake oil these days.:laugh3: Maybe a larger dia. throttle body instead, but they are a bit pricier.
Depending on the year of your XJ, swapping your factory ex. manifold with a set of after market headers.

Then there's always Avenger...

Tim

You can add a bored out Throttle body, a set a free flow headers & exhaust, to the K&N FIPK, or Rusty's air tube, will help alot. If you do the air tube, just shield the filter elemnt from the engine bay heat.

Rob

if you do homemade fipk intake, mabye home ported head?bored tb, exh. header/downpipe/new cat/catback will flow enouth extra air that the motor will need bigger injectors. R.Rockers=$$$$ pretty much all you can do w/o forced induction or getting into the short block.