I'm servicing a Trane YCD048C3L0BF gas package unit (installed Q4 of 2000). The customer complaint is not heating properly. I found the gas valve is woofing. A digital manometer shows 10 at the inlet and +.20 wc at the outlet. I'd like to adjust the pressure on the gas valve to obtain required -.20 wc.

Snap ring pliers aren't cutting it, but I'm not sure what spanner wrench to buy, not only for size, but for usage inside the confines of the cabinet. As you can see in the image, the angle of the holes in relation to the CF blower wheel housing and the cabinet seem to require a specific tool design. The equipment manual suggests the snap ring pliers or a paper clip (heh!), neither of which are up to the task. Any suggestions appreciated. Image below:

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Also, what other symptoms can high outlet pressure cause?

Thanks,
Vin