Codes 41 and 91

I posted this in an old thread which confused some. So here it is in a new thread.

I Have a 347 with long tubes. New ACT, coolant sensor, MAF, and bosch 02 sensors, IAC. Sometimes it idles great and sometimes it is loopy and dies when I come up to a stop sign.

I keep getting these codes 41 and 91. I have the orange ground to the intake. When I test the wires to my 02 sensor (after unplugging I get 12v on the hot wire and continuity to the ground on both harness.) I have probed the ECU. On 29 I originally had 0.5v (positive) but then it slowly fell past 0 to -0.4 (yes, negative). I measured 43 and got a negative number as well (it fluctuates but remains negative). (red to the ECU and black to ground and I checked at the battery to be sure the polarity was right and the voltmeter was working). I'm not sure what this means. Any ideas?

-Mike

My ground and hot are fine. Heating elements should be good since they are brand new (be wierd for both heating elements to be out on new sensors). I just used my voltmeter to measure my TPS and it's working fine. I do have another meter though I can try. Anything that would cause a negative number?

- Mike