Timing question....again

[nj240sx]

ok well I've done the whole warm up the engine, rev it 2 or 3 times, disconnect the tps, then set the timing...ok fine done no problem. it's advanced 15 degrees it looks good. Then I plug the TPS back in and double check it and it nolonger lines up... it's a S14 SR20DET so is this normal? car's been running alright for the most part, other then boost creep issues .