I have a similar problem I had a ulev vtech and swap for a non ulev vetch I replaced my intake manifold on my non ulev ( put the ulev on it) now the issue that I have is that I'm getting p1519 ( idle control valve/circuit) my Rpms are going up and down like a vacuum leak I check all the hoses cleaned all the passages on the air I take plenum , replaced the icv sensor with one of a running car and same problem then I traced and test the power12v , ground and feedback wires from the sensor all the way to the ECM and they were ok I even ran new wires and still have the same result , wondering if I have to replaced my ECM (should be my last thing to do) the ECM is from my ulev . Any feedback will helP thanks
M