94 100 2.8 V6 issues

[dgraber460 at aol.com]

Oh great list of wisdom;
A friends 2.8 V6 recently broke the belt and bent the valves on the passenger head. the driver side head compression test was to spec so we only pulled the passenger side (budget constraints are in play here). We pulled the head, had a shop throw some valves in it and do a cursory check for other issues. We then put it back on with new gaskets, belts, t-stat, and water pump. It fired right up after reassembly, and we used the proper cam alignment bar when putting it back together.
It will not run properly until warmed up. Idles OK, but no power till warm. 
It has been throwing two O2 sensor codes. "Regulation", "Regulation2". The plugs are nice and clean with no sign of richness. I'm guessing it has a temp sensor issue and doesn't richen up for cold running? But it starts well when cold. Confusing.
I'm familiar with the I5's but not the V6's. Which sensor (or system) do I start with to figure this thing out? Yesterday it acted up after warm and lost power for a time on the highway. Their descriptions of the issues are a little difficult to interpret.
I'll check the codes again this morning (cars not here yet this morning) but I need a diagnostic step by step to get this figured out.
Any help greatly appreciated.
TIA

Dennis 
Denver