TPS % changing at same voltage???

I have the tps set to a voltage of .55 and when a reset is performed the tps % will stay at 0 for several minutes but if it idles very long % goes up to around 4% and the voltage will still read .55???

Any insight to this, I can post a log and the tune of needed but I don't feel its tune related.

98 trans am with Fast 92 intake/Throttle body.

Try 0.49v instead.

0.55 is on the high (idle) side + you have a bigger aftermarket intake, so maybe after you do a TPS reset and get it to 0%, the computer/whatever slowly increases it to what it's sensing and is a little confused.. ? Is your warm idle high? I'm guessing it is..