Do not use a IVR with aftermarket gauges. The IVR drops the instrument voltage down to ~5volts, and aftermarket gauges require a full 12V. If your aftermarket gauges are bouncing around, you may have a bad connection or a short somewhere. Get a hand held volt meter from Radio Shack or elsewhere and check the voltage going to the gauge.
Dynacorn 67 fastback. (The money pit)
'14 SHO with most all the bells and whistles. Stock for now.
'97 TBird project. AED supercharger, forged bottom end. Runs high 11's, when it runs.