Re: TB Spacer worth doing?
I haven't run mine on a dyno - yet.
But I have done before and after tests on other cars, TBI and carbed, on chassis dynos. Sometimes it helps quite a bit, sometimes not much.
Partly it depends on how bad the intake was before adding it. If it wasn't keeping the fuel atomized enough it'll really help. Sometimes figures get distorted because at the same time it's added, adjustments/improvements are added to ignition or something else - which really helped?
Seems like I've seen 20 HP improvement sometimes, and sometimes nothing.
Somewhere around 5 hp is where your seat of the pants start feeling it. Of course on a 600 hp motor 5 isn't enough to notice, but on a 100 hp it's significant.
The Jeep's 4.0's are around 180-193 - so 5 is right on that edge.
I added the "Rock-it" airbox eliminator with the K&N, it's supposed to add 5-8 hp. I definately can "feel" that. Not a bunch, but it does help.
I have the smooth bored Port Injected spacer, it's supposed to add more too - it's awful thin, maybe 3/8" thick. I can't believe so little can make a difference, but we'll see. I haven't put it on yet, I'll advise when I do.
Too bad there isn't a little trick or an easy bolt-on that'll give another 200 HP, that would make it fun!