99+ Intake Manifold upgrade on a 1996 XJ 4.0 and other Air & Fuel upgrades
To make a long story short as to how i came to this upgrade, My 02 sensor was reading a lean condition. let's just leave it at that. This Tek will show you what you need to do a 99+ intake upgrade to your '91 to '98 4.0. This is NOT a full detailed "how to" but is a general idea. please note: this build info is for a '96 to '98 4.0. Most of this info can be used on '91 to '95.
First lets get the parts list out of the way.
1991 to 1995 build list		1996 to 1998 build list
99+ Intake manifold		99+ Intake manifold
Intake gasket - Fel-Pro #MS94790		Intake gasket - Fel-Pro #MS94790
your fuel rail & injectors		your fuel rail & injectors
'96 to '01 PS pump and reservoir
'96 to '01 PS pump bracket with idler pulley
serpentine belt (unknown length)		My additional parts to this project
Possible PS pulley ?		Edelbrock Ti-Tech shorty header
		Fastman 62mm bored and machined TB
		Precision Auto Injectors
		K&N Air filter
		Air flow Snorkel
Links for this project.
Fastman bored Throttle bodies		Edelbrock Header #65923
P.A.I. Upgraded Fuel Injectors		K&N Air filter
Gibson Airflow Snorkel		Oreilly/Checker Auto
Ace Hardware		Ebay Motors
		I went thru and tagged everything so its easy to re-assemble. You also want to make sure you keep the Injector wires correct. I was able to leave the injector harness attached to the head. you may be able to do the same.
		Remove intake manifold as the manual instructs. You can actually leave the two nuts at either end still on. All they do is hold the exhaust in place.
		The pressure line for the fuel had an internal clip lock that required a special tool, kind of a donut tube shape tool. $6.00 at checker and i nowhave a whole set of them.
		You now have access to your exhaust manifold. For me its coming out and its being replaced with a Edelbrock header.
		Not much to these things. This was all about an hour and half. your results may very, especially if you live in the rusty areas.
		The one thing you should do is if this is going to be a long term project like more then a few hours. I suggest taping up the port holes on the head. This gives you less chance of getting debris inside.
		These are common spots for these headers to crack
		Cracked at the collector on one side
		continuing almost all the way around
		Cracked between ports 4 and 5 on the inside
		Ahh, new header. All nice and shiny. The tubes are not matching in length but they are better then the factory ones..
		You can see the improvements int he collector. Its more uniform
		Another shot of the new collector area.
		A none Chinese product! Lies I say!
		I finally received the 99+ intake off of E-bay. It turned out to be a lot worse than i thought. This was going to take some time cleaning.
		I suspected this intake came off of a blown motor or something the entire inside of the runners and plenum were pure gunk and carbon. I have never seen an intake this bad. Ports #1, 2.
		Another shot. Port #3
		This is about 5 hours later of power washing, Scrubbing, 3 cans of Carb cleaner, 2 cans of brake cleaner and sandblasting.
		Ports #1 and 2 you can see the difference.
		Again, Port #3
		A quick shot of the intake partially assembled. I got a hold of a TB spacer that just happened to be bored out to 62mm as well
		Both the TB and the spacer matched the intake base. One HUGE 2.440" hole through and through. Click here for the fastman TB comparison I did.
		Cleaned up the gasket surface using a angle die grinder with a medium scotch-brite pad. I then wipe off the surface with starting fluid. I also wiped out all the ports just in case.
		Installed the new header. It has a nice amount of clearance all around. This header uses the factory flange to mount to the original exhaust.
		Re-assemble the intake as the manual instructs. With the new header the the two lower bolts in the back had to be done in a combo underneath and above. they were a PITA.
		Fully assembled with the new injectors.

Update: 5-2-09

Initial results are very impressive. This build was originally planned to gain power in top end but I also gain some in the bottom as well. Power at highway speeds is more prominent and when I give it gas it actually accelerates. I have not figured gas mileage out yet as this tank has been a lot of idleing, reving and highway passing.

Prior to this project I could only drive in 3rd (with L/O) at 65mph at around 2500rpms. I had a vacum guage hooked up and was pulling around 4 to 5" inches in vacum. Now, with same variables I am doing around 10 to 12" of vacum with less throttle.

This is a OBDII system. I just had to drive it for a couple of days and the ECM learned the new air/fuel and exhaust setup. I have a Full live ECM scanner so I just drove until the scanner showed all ok and it passed emissions just fine.

I will try and get an update on fuel mileage in about two weeks. I have a Jeep event to attend.

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