Hey, welcome to BC!
You may have another manifold problem. Could be it wasn't installed correctly. Check your oil, does it look milky? Smell your exhaust, does it smell like its burning coolant? If you have coolant in your oil, GET IT DRAINED ASAP!
Steam coming out in cool weather? That happens to me early in the morning after I stop. Condensation builds up on the hood, when I stop, it rolls off the hood, goes into the radiator area and hits the hot radiator.
Misfire? Try moving your #6 wire away from the O2 sensor wire. Seen one member do that and it stoppped.
Report back to us on that coolant please.
1997 Pontiac Bonneville SEi-SCRAPYARD
2000 Chevrolet Blazer LT 4X4 4.3L
2002 Chevrolet *-10 LS Ext Cab 4X4 5.7 V8