O2 codes at open loop?

[Nixon1]

The other day I got in the car to leave from work and made it around the block before a Check Engine light came on. It would go out for one or two seconds, then come on. Mostly under acceleration. I pulled into the Autozone because for one of their free diagnostics (dont want to buy a code scanner, and I know how to use a paperclip to pull GM codes, but not Ford codes!)... Well the codes came up as 41 and 91, which I was apprised were Left O2 lean, Right O2 lean. (Voltage low.) Now this surprised me because the car hadn't reached full operating temp yet. It SHOULD have still been running open loop operation.

Two days later, I get in the car to leave again, and after idling for about 10 seconds, Check Engine comes on. I turn the car off, and turn the key to Ign. to reprime the fuel pump. I do this twice, then start the car. It idles fine, with no light. As I go to leave the parking lot, I tip in on the gas and the light comes on. Every time I hit the gas pedal, the light came on. I didn't have time to pull THAT code, but I assume it's the same code since the only other code my car has EVER thrown was an MAF (out of range) code from running air filter-less.

What would cause my computer to try to read from the O2's prematurely...or what would cause it to even try to go into closed loop before it's ready? I thought AT LEAST the CTS had to read something like 140 degrees and both O2's had to be hot enough to send variating signal voltage.

The only things I've done to the car recently are remove the oil filler cap and PCV return line, block the manifold fitting, and run a breather (valve cover baffling removed, allowed oil into the return line)....and my evap system is currently open-ended. There was a pinhole in manifold line there, so I plugged the manifold fitting. I was going to buy more vacuum hose, but the fitting on the sensor that the gases pass through snapped off, so I left it open. Also note, the car was very low on fuel...the needle was right above the empty mark. Could this have anything to do with my problem? I can't imagine any kind of vaporlock induced by running an open-ended and not an actively pulled evap system, since EFI motors run high line pressure.

I checked my fuel pressure after the codes and, of course, I couldn't get the Check Engine light to come on again. Pressure read 42 at idle, and MOST of the time when I revved the motor, it would spike up to around 48 or so. Although sometimes the pressure would DIP instead, down to about 39. New injectors, AFPR installed.

Sorry the post is so long, but there's a LOT of details I wanted to include. Any help is appreciated. My motorcycle just got hit so it's in a repair shop right now, and I can't afford to have my only other vehicle break down!