Well I may have stumbled onto something...I was getting air bubbles at cold start when I checked it last night. I looked very carefully over everything, and noticed one of the braided return lines was weeping through the casing (I must have flexed it too much when putting it on). I put another length on and ran the car for a few minutes to get any trapped air out. I let it sit overnight and when I started it this morning it didn't miss at all. I'll monitor it the next few days and see if that was it, but I would be pretty happy if it was that easy of a fix lol.

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97 S500 (90,000 miles) - wife's car
87 300D (298,000 miles and a replacement #14 head)
94 Suburban K2500 - need something to haul firewood
83 300SD (343,000 miles) (sold)