We ordered a new genuine Mopar replacement O2 sensor from Quadratec (PN 55120.03). Unfortunately, we ran into some fitment issues with the replacement exhaust manifold. The flange is a tad thicker than the ’89 2.5L intake manifold, which prevents the intake from completely sealing against the cylinder head. We had a major intake vacuum leak when we restarted the vehicle. We’ll pull the exhaust manifold back off and will figure out the solution for next month’s column.