4.0L XJ question

[FYR WOOD]

I know its not a FSJ, but I need to know and you guys are the only ones I trust. So...what is the difference between the 4.0L and the 4.0L High Output? There must be some difference because simple tune-up parts do not interchange. What years did the H.O. come in, and will it bolt right into my 88 non H.O.? Anyone got one for sale?

[Navajo]

'91 and up was the H.O. It has a better head, less restrictive. Thats all I know. But its a start.

[Sycho15]

The fuel injection chaged to a more efficient system in '91. There are many other small differences but nothing to really worry about. I'm running a '97 4.0 (2nd Gen HO) in my '89 Comanche (non-HO) with the original Renix EFI system.