Reiver

spoiler: made a huge difference.
930-10 euro wur on an '83. The SC wurs on Euro's and the pre lambda US SC's control your AFR thru a vacuum system.

My car ran very well, started great, idled perfectly but would not enrich the mixture at wot event tho is still ran strongly. If I didn't have an onboard AFR I'd of never suspected an issue.

Sent it in for a test rebuild or exchange.

The old one was out of spec but close enough to make the car run well as the CO had been changed over time to compensate for the lost spectrum.
The diaphragm's had lost their flexibility and became hard with age.
I had the AFR set at 13 and would cruise at about 14. When stomped on would see 14.5-15 so it still ran well.

New wur. Stomped on see mid 12's and cruises at 14.7 AFR...

The difference I feel in my butt dyno is dramatic. Going to wot in 3-4-5 the nose of the car now physically lifts on accel (yes, I have new shocks Iceman).

Feels like another 20-30 HP (I know it is not but feels like it).

I suspect the difference wouldn't be as great on the US spec lamda models as the lamda controls the afr I understand....but that is a guess.

Getting the fuel delivery into proper spec made a huge dif.