we have a 2004 350zs ZR, its automatic and ive noticed that when i put it in manual mode while in first or second i give it a bit of gas and it revs and accels obviously.. if i let off the gas the rpms drop and then rev up to like 2.5k without me giving it any more gas and then it drops back down to idle, im pretty sure it does this in neutral as well any ideas what may be wrong? or is this normal?

 

It is normal for the rpm to spike back up a little when you let off the gas but not to 2.5k's.