Reading several posts on this sight, I've seen it mentioned that the somewhat common Regina rough idle issue can be improved by an increase in fuel pressure. A few days ago someone said there was a recommended retrofit regulator that supplies increased pressure at idle (high vacuum condition). I beleve he said the later model Regina 940's had the alternate regulator as original equipment. At least I THINK that what he was saying. After reading that, I tried disconnecting the vacuum hose from the regulator and plugging it. I dare say that when I drove the car it did seem to idle smoother, especially with the A/C on. It seemed to run well at all throttle loads, but I didn't drive it around a whole lot in that configuration.

What I'm wondering is how much richer was it running, and the overall effect on fuel consumption, and would it pass emissions testing that way. Wouldn't the O2 sensor read and call for the correction of any over-richness? Under high throttle load (low vacuum condition), it seems the difference would be negligible.

Does anyone know of a table or graph that describes the vacuum vs fuel pressure relationship? Also, can anyone confirm an appropriate regulator upgrade?

Thank you.