ive got an 87 xjs with the he engine, i know what everyone says that the he cant make you any power, but im going to try anyways. i want a milder road rally cam, bigger throttles, ( or possibly quad throttles) growler style intakes and i already have removed the cats. whats everyones thoughts? and i plan to one day build a he engine so money spent isnt just thrown away if it doesnt work ill just save if for the 500 hp v12 i would like to build

 

I've been studying this myself, so I've got some numbers to give you. Of course, these are the claims of others and I cannot verify them.
Removing the mufflers and resonators and replacing with free flowing mufflers is supposed to get you up to a 35 HP increase alone. I suspect removal of the cats will help some as well.
Headers are available, but from the research I've done, there isn't any significant power change.
Altering the stock ECU to a MegaSquirt system and re-configuring the injector sequences and duration, plus changing to larger injectors with larger TB's and cold air, low restriction air filters can net another 30 horse.
Cams are available, but really have a detrimental effect on the low end (0-60) so you really won't gain much unless you're traveling up on the high end of the RPM's.
Dropping the rear-end ratio can decrease the top end, but gives you a faster 0-60.
Removal of the air-pump gives another 2-3 HP and replacing the stock cooling fan with an electric boosts another 4-5.
Hope that helps?

 

yeah, i got highflow cats from the drivenman system and i also am getting bigger pipe that dumpes under the middle in the rear end. i am lowering the rear end from 2.88 to 3.31 or 3.54 and i am using a t5 with a very deep first gear so getting to high revs isnt a problem. the cams give you 15+ horsepower gains they just shift your power curve upwards

 

and im building the coldair intakes, as well as getting a remapped injection system to go alone with all my new stuff, and hopefully the aj6 throttles, id like to hit in the high 300s cant go any higher than 400 or i will blow up my transmission. haha
also ford edis6 units are supposed to give you 20 hp gain,
Dual EDIS ignition