I just bought one for my 88 lx 5.0 , and it fixed my idle jumping up and down problem. I did not experience any of this high rpm you talk about. If you have an intake vacuum leak , it will rpm a lot higher than that.
My new one looks just like the old one. I tried cleaning my old one with rubbing alcohol and qtips and it made it worse (first time i attempted it).
Oreilly autoparts has the same part for 55 with lifetime warranty compare to 41 with 3 month warranty from twilight zone.
I've replaced almost every part of my car. It used to do the rpm fluctuation on my old motor too so I know it was something tagged onto the new system.
89 GT Hatch: Custom M90 Supercharged w/ Ported Trickflow Trackheat Heads, Stage 1 cam, Streetheat lower / Sheet metal upper, Tweecer RT & PLX Wideband, 75mm TB, 1.6 Roller rockers, 3.73s, MSD 6a, Canton 7qt Pan+ Windage tray, 36LB Injectors, 200 amp Alternator, 75mm Pro-Mas MAF, 190lph fuel pump,Spec Stage 1 Clutch,SouthSide LCA's, Pro 5.0 Shifter, Steeda CC Plates / Springs, FMS Aluminum Driveshaft, New T5 w/ 2.95 first gear, Underdrive pullies, Zirgo 3300Cfm Elec. Fan, AFCO alum. radiator