P0340 cold start on 2.7

I'm getting an intermittent P0340 Camshaft Position Sensor error. It only happens on cold starts when the temp is low 30s or below. If I turn off the CEL (clear codes), it won't come back until the next cold start after overnight temps below 35 or so.

On my '96 3rz, the camshaft position sensor is in the distributor, so replacing it requires a whole new distributor. I replaced the distributor with OEM about 40k miles ago, and now the error is back. I'm thinking maybe something else is causing this, but don't know where to look.

Any ideas on what might be causing this?

 

bump. Someone has to have dealt with this before. I really don't want to keep throwing $400 distributors at this truck.