Miscellaneous information:

(Hi. 1990 740 GL, Regina, nothing fun done to it. Had a timing belt go a month ago and I've only now gotten it running reliably (long, sad story).

After changing the timing belt, it's started misbehaving. Idles okay (not fantastic but not bad enough to worry, IMO), but even in park it starts missing under any kind of load.

Changed the fuel filter and that helped - it was older than I thought and was partially clogged. Still running funny though. Idle motor is clean and working fine, on at idle, off under any other conditions.

Tested the FPR, and it flows gasoline copiously at idle, but under load it puts out almost as much gas. It's at least trying to close, as the stream does lessen noticeably, but it's still a high-velocity jet and I could only keep the car running for a few seconds.)

Actual Question: Should the FPR close completely under a sudden drop in vacuum? I revved it from idle to ~4000 during my test and it was clearly still mostly open. I know when they fail they can close completely but I'm not sure if that is part of its normal operation.

Thanks! Hoping for good news...