Just put the motor back in the car. Having a couple of issues.

Doesn't matter if I'm doing 50kph or 100kph. As soon as I take my foot off the gas the RPMs drop down to 900 rpm almost right away.

What could be causing this? Vacuum leak? Header leak?

Also the car seems down on power a bit.

It rattles sometimes when I shut it off. Sound seems to be coming from the back of the motor. Idle seems a bit low too sometimes.

No codes showing.

 

doesnt sound like a engine issue to me when my transmission started to go AFTER i had it rebuilt by some idiot...it to went to an idle when i let off see if it raises the rpms when u down shift

 

Yes the rpm goes up when it downshifts. I was doing about 20mph and when it downshifted to 1st the rpm went up to 1200 rpm from 800 rpm.

Usually the rpm drops when I'm in 3rd.