I'm not sure what brand of tranny fluid they used. Could that make a significant difference? Idle speed at startup is about 2500 RPM (cold) and 600-700 RPM (warm). I have been having codes for the O2 sensor again, causing the rpm to drop too quickly btwn gears and sometimes stall at idle. But that I will soon fix myself, and assume that is unrelated to this issue. When having this issue, the rpm is not elevated at all. Should I have the tranny fluid drained and refilled with a proper brand? Thanks.

99 Black SVT -3L Hybrid w/.5mm overbore, Spec clutch/flywheel, MSDS, BAT intake, K&N open, 17'Konig Tantrums, DMD, Opt. TB & Y, Powerslots, Bassani w/ magnaflow res. 96 SE MTX- "The War Wagon" "I'm in love with my car..." -Queen