Vacuum and engine performance and mode switch

[Timebender]

I know that losing vacuum can cause engine issues - especially on a 350 sbc setup - I accidentally knocked the main vacuum line loose and lost power brakes and the engine ran horribly.
So I'm wondering and maybe this has some truth to it, if the AC mode switch can affect engine performance when it's on. I did have a small vacuum leak at the hose that connects to the lower canister on the driver side, and fixed that, but I do hear some whoosh sound as I move the mode switch - and when I first tested it it mostly did its job of opening and closing flaps (which was pretty cool to watch). But now it's not doing it so much, and I do hear something from behind the console when it's in any on position.
And since then my engine, when running at least, has been acting up like it's a vacuum leak.

So can that cause enough of a vacuum leak overall?

[DMCMW Dave]

I know that losing vacuum can cause engine issues - especially on a 350 sbc setup - I accidentally knocked the main vacuum line loose and lost power brakes and the engine ran horribly.
So I'm wondering and maybe this has some truth to it, if the AC mode switch can affect........

So can that cause enough of a vacuum leak overall?

I don't think you'd ever see it. I've heard people say it can cause a lean condition, but it's a pretty tiny leak (less than 1/8" hose about 5 feet long)unless the hose is completely off.

It's easy enough to cap off the vacuum hose and find out. The main feed is the large hose that goes into the pontoon on the left side (it tees off the passenger side intake runner, the other side of the tee goes to the brake booster). You can pull the hose apart at the check valve and plug it towards the engine. Or just disconnect and plug the small line at the mode switch.

[Timebender]

First thing I'm going to do is replace a bunch of stuff in the distributor at one time- or just get a new one and then go from there- test the vacuum stuff, etc. , though when I did fix the hose to the lower canister then turned the mode switch, the car did die. Coincidence maybe...