Bad WUR?

[Mac-Porsche]

Been having cold start issues for a while. Engine takes a while to start up (turns over ~3 times before firing up), then runs poorly when cold. Low, surging idle and sluggish to accelerate, etc. Once warm, engine runs great and starts up instantly.

So I checked the control pressures on then engine when starting from cold (sat overnight) and noticed that the pressure goes to ~1.4 bar (bobbles a second there) then to 3.4 bar in about 20-30 seconds. Stays flat at 3.4 bars from then on.

I checked the resistance on the WUR (I assume I'm correct in checking between the two pins?). The reading shows 10.2 ohms. Re-checked several times to be sure, same answer every time. This is with the engine cold, having sat overnight with no starts before checking (not sure if that matters).

This is a US '81 car. WUR is a -090. I keep the 02 sensor unplugged (for richer mixture/power).

I've read it should be over 18 ohms. Does this mean the WUR is bad? Anything else I should check or try?

It's stored in my garage where it's at 78°F - double checked WUR temp with infrared thermometer also shows 78°F.

(Few other comments maybe worth mentioning... System pressure is 4.5 bars. Residual pressure checks good. Set the warm idle AFR to ~13.3, CO% is at ~3.1 which was intentional for power. Rebuilt engine very recently, only have ~400 miles on it, 97mm P&C's w/ 964 cams & SSI's. Gas mileage is terrible, 13 mpg. Wasn't sure if this was because of the richer mixture or something else.)