I own a 99 XJ looking to get some more horsepower out of my 4.0 what are some things that are reliable and efficient.

 

Here's a couple that are easy:
63mm bored tb
784 injectors
snorkel (it's a true CAI)
gibson headers and a 2.5" exhaust with a flowmaster exhaust
resetting the ECU after each/any combo of these are done.

 

Ive heard mix results about chipping this motor which if any are worth using.

 

No, what you really want is torque!

 

hardware mods only.

larger throttle body
free flowing exhaust
cold air intake
injector upgrade to 4 hole (better atomization / throttle response)

on the more severe end:
stroking the engine:
camshaft changes
bored pistons
etc etc


however i would start with a very thorough tune-up:
plugs, wires, distributor cap, fuel filter, air filter, fluid changes, injector cleaning, seafoam application, etc....you'd be surprised how much hidden horsepower and throttle response you will uncover.

 

thanks for all the info ill let you know how it all goes.

 

You never let us know how it went?