I have a 99 civic I swapped the motor for a 98 Y8 motor. I read up here to jb weld the hoes on the manifold cause it wouldn't work right. To you think the jb weld could've wore off an starting to make my car idle an pickup speed slow. It ran perfect right after the swap it was quite an didn't idle. Did a fresh tune up 3 days ago, oil, plugs, wire etc. an by it not being enough pressure build up in the manifold could that cause it to run this way?

 

jbweld doesnt wear off. its like cement. pics. not sure what your even saying.
check rotor and dizzy cap? tps functioning right? codes? what ecu?

 

Check your map sensor voltage and tps sensor voltage, they could be the culprit.