In the past week, my 96 850T idles funny, only in park with a warm engine. It drops from a steady 900 to 800-700, then surges above 1000rpm, sometimes as high as 1500, then drops back down to a steady 900. It will do this every couple of minutes. I've recently replaced the tourque mount with an OEM, I say this only because I removed the intake hose and cleaned this out. Maybe I damaged the PNP switch? I also did a tranny flush, and replaced the ABS module with one from a '95(which works fine).

Could I be in need of new vac elbows? Fuel pump? I recently had my codes read, nothing showed up. Maintenence up-to-date, 155K miles. Any suggestions?