thanks to all for the great suggestions...I did put the skinny hose/pipe/whatever back onto the bottom of the air cleaner (it attaches to the plastic thing that sits in the middle of the air cleaner), but I also changed the large fuel filter (I guess that's referred to as the secondary filter, as it comes AFTER the little transparent one in terms of fuel flow) and that made all the difference-once I actually got the car started, that is...

I didn't have any diesel handy, but I had some kerosene, so I put an ounce of so of MMO into the filter and then filled it up the rest of the way with kerosene. Pumped the primer pump (which is a new Bosch one I put in and seems to work very well), but the car just didn't want to start for about ten minutes of trying (giving time for the starter to cool down between tries). It's NEVER been hard to start-even in single digit winter weather-so I was worried for a bit, but I thought maybe it just wasn't happy with the kerosene..once it finally started I let it warm up a couple of minutes and drove to work, and all was well-it ran like it should.

The thing that threw me off was that before bringing it in, it was running fine; I didn't think the dirty/clogged fuel filter would *suddenly* bog the car down that much, that quickly, so I was looking for other reasons. My only theory is that perhaps removing the tank screen to clean it might have dislodged some sludge/goo/gunk that then made its way into the filter when I drove it home from the garage. Or maybe that's just the way it goes with those filters...great, good, good, good, dead LOL

sorry, but I don't know all the terms mentioned in the replies (elbow pipe, wastegate arm, switchover valve, ALDA, etc.). I'm really pretty ignorant about most of this stuff. I'm trying, but I'm old and getting stupid fast...