I have a 91 Xj I put a 99+intake on it with a header and a 62mm tb and I lost power I can't figure out why everything I have seen says other wise I reused the injectors off my old intake because I have already upgraded to the 4 pintal ford ones I also put a new o2 sensor on it I broke the old one when I tryed to take it out of the old header if any one has any tip it would be great

 

make sure all the vacuum lines are connected correctly no leaks. all sensors and injectors are hooked up in the correct order. if youre still having problems id check to make sure the injectors are working properly.

 

I have smoke tested it no vacuum leaks hooked up to obd1 scan tool all sensors reading correctly so everything should be hooked up and I don't see anything unhooked and all my injectors are working correctly I bench tested them

 

I did the same swap. I left the 2 vacuums on the intake off. I plugged the vacuums on the intake. Except the brake booster of course. I still had a loss of power. Finally I found my prob. It was a combo of a bad fuel pressure regulator, a bad map sensor and some how a bad pcv valve. Hope that helps.

 

How was your PVC valve bad a 4.0 dosnt have one it is built in to the valve cover and I already put a new fuel pressure regulator on it and I check fuel pressure it's correct and the map sensor is showing the right voltage I have spent some time on this and I just can't figure it out I even gasket and flow mached the intake runners when I did it

 

I have heard the certain brands of o2 sensors don't agree with jeeps anyone have any input on that I have a direct fit bosh one on there now I don't know what was on there before but the ends of the o2 sensor did look different

 

Because when I done the swap I needed a new house going to my map sensor haha. I found one lying around the garage and it fit. Come to find out it had apcv valve on it. It screed my idle all up. Lol.

 

Yea that would cause some problems mine runs just fine it just is slower and you can feel that it wants to go faster it just feels like something is holding it back but it idles fine and dosnt miss or anything