On the 9700 card, I did not tape the pins, since I have a Sawtooth (non-ADC) it does not use pins 3 and 11 for whatever purpose the ADC Macs use them for, so I was told it was not necessary.  I also believe mine is AGP 2x, but could be wrong.

On the 9000 cards, they are definitely Mac cards.  One is labeled as such and both have the extra spade connector and ADC outputs.

I will try to clean the slot, but can't figure out why the GeForce and R128Pro work.  Unless these cards don't like to step down to 2x.  (there is a post in the forums of one guy saying he did this.)