Heat sheilding intake

I've been wanting to do the same thing. As far as injector positioning I don't think it matters whatsoever. Though I did end up damaging two of my injector o-rings from twisting them too much which made them leak. I'll actually void the warranty on my headers if I wrap them so I'm guessin there really is a good reason not to wrap them. As far as the intake manifold however, being aluminum I don't think it would hurt them.

Wrapping headers does seem to make them more prone to cracking. If you are worried about your underhood temps, I'd do some hood vents (Chrysler Lebaron ones are popular, but there are many options people have done).

I would not wrap the X if you craw or tow. Long times at slow speeds and high loads would let the X and the X value over heat.
Wrapping tends to work at the 1/4 because of the short time the engine is under heavy load. Also 1/4 people are use to short engine life and live with it. At speeds air moving over parts help keep thing cool.
A high flow muffler tend to help get the heat out of the engine and engine bay. Vents are also good at low speeds. A trany cooler NOT in front of the rad or engine bay can help.
If your after more HP by cooling the intake. Try cutting the webbing between the runners on the late model intakes. But this has caused a bog in the coldest part of the winter (10 deg. F and lower) for me.

IIRC GoJeep has a web page on an under-intake heat shield he cut and installed, with before and after temps. Looked worthwhile.

I second the idea of not wrapping the exhaust, most reports say it's a "great" racing idea, but rusts out the header in half the time. The power increase is pretty minimal on a Jeep, if at all.