Oh cool, thanks for the offer. I'm very close.

I had thought of an exhaust restriction but can't see how that's possible with no cat. It seems like there would have to be some extreme condition to cause something like that, or ultra high mileage maybe. Im under 200K. Anyway I didn't see any obvious way to get a peak into the manifold area yet.

I was only able to replace the filters today and there was no difference. I will try the bypass tomr and hope that solves the mystery... getting nervous!