3000 rpm?!

[Rawr..!]

My holden commodore VT has currently had a new engine put in,, Since then I have had trouble with the gears, I THINK, in fourth - or third? Im not 100% sure it even changes.

It's doing 3000rpm going at 110kms therefore chewing through fuel. I understand that it should be just a little above 2000 at 110km.. When i take my foot off the accelerator but stay on 110 the rpm goes back down to where it should be..? It also changes back into third if I use the lever to put it in three (it's auto)..

Can anyone tell me what the problem might be..? I am trying to save a bit of money so I'm hoping someone will tell me the most likely problem so I don't have to pay someone to look at it for me :/

Help..!

[Rawr..!]

Just as an extra note,, I read up about it, I'm thinking it may be the throttle sensor? Your opinions?

Thankyou (:

[Tsunamix]

Revs should be 1850 in top at 100. Im having a think about your problem will see if I can figure it out. TPS is not the only thing that affects changeup