I don't think it will run well without a cat. Everything is ECU/computer controlled. Removing the cat will throw the O2 sensor values off and the ECU will try to compensate by adjusting the fuel/air mixture. And that won't make it run better...

The resonance chamber(s), if I recall correctly, were added to absorb/cushion the airflow being disrupted by back pressure from the intake valves opening and closing at various RPM in combination with acceleration/deceleration. I pulled mine for a while. But I reinstalled them when I had to get my Sporty smogged (Cali requires a visual inspection in addition to testing the emissions at the tail pipe <img src="/forums/images/graemlins/baby.gif" alt="" />). I didn't find any improvement in performance with them installed or removed. So I got lazy and left them on after the last smog check. No harm either way. You can cap the opening on the cross pipe with a plumbing-type expansion plug (rubber kind). But it doesn't help smooth the airflow through the cross pipe. If anything, it may add some turbulence. Again, I didn't find any change in performance... beyond invigorating my Speed Racer fantasy while driving my Sportage Mach 5... <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

Last bit: The coils make contact with a metal cap backed by a small spring - all of which is retained on the coil by the plug boot, if I recall correctly. The bolts hold the coils in place. The spring maintains the contact. There's no snapping into place like you get with a standard plug wire/boot. If you lost the spring on one... that could be a problem.

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1997 Sportage 4x4, auto-trans, Warn manual hubs, 4" UPYOURKIA front lift, TJ 106AA rear springs, 2-5/8" body lift, 31x10.50 treads, SmittyBilt SRC front and XRC rear bumper, swing-out tire mount, OBX LSD front diff, Track Finder rear locker, 5.38 R&Ps and... really crappy gas mileage! <img src="/forums/images/graemlins/shiner.gif" alt="" />