Search "Hesco" for top of the line and insanely expensive 4.0L upgrades.
decent gains can be found using junkyard parts. an Intake manifold off a '99+ 4.0L combined with a tubular exhaust header can give you a good boost.
for real power gains you'll want to add forced induction, or better yet stroke the engine using a crankshaft from the older 4.2L to make a 4.5-4.7L+
Good info on upgrades can be found at
www.naxja.org for XJ cherokees, www.nagca.com for grand cherokees.
do a ton of research before spending any money to decide if it's worth it.
hope this helps get you started,
-B
decent gains can be found using junkyard parts. an Intake manifold off a '99+ 4.0L combined with a tubular exhaust header can give you a good boost.
for real power gains you'll want to add forced induction, or better yet stroke the engine using a crankshaft from the older 4.2L to make a 4.5-4.7L+
Good info on upgrades can be found at
www.naxja.org for XJ cherokees, www.nagca.com for grand cherokees.
do a ton of research before spending any money to decide if it's worth it.
hope this helps get you started,
-B