thanks, SubGothius, that is super helpful. i also tried turning the distributor rotor on the parts truck, and it doesn't turn either, so unless they both are rusted tight -- i guess there's intentionally no advance? as for the timing being off-- what i think is going on is that the timing was set way advanced previously, and it was kind of working but had low-RPM problems (which kind of makes sense). i then timed it "properly" with a timing light using the numbers on the plastic housing, and it's now got the problems i describe: terrible loss of power when attempting to revv, and backfiring. which i think makes sense if either a) it's not advancing enough with increasing revvs, and/or b) it's leaning fuel (due to pressure or other things). (am i thinking this correctly?)

so -- *could* it be a slipped tooth on the timing belt? which might mean that my timing light-setting is way off? would there be other symptoms?

or could it be that some sensors (which ones?) are causing the computer to send completely wrong advance info? (when the computer is engaged, the timing jumps around randomly within 5 degrees every rotation, it seems like, not sure what that means.)

or, of course, could just be low fuel pressure maybe? claych offered to talk to me about how to test that (thanks), but any thoughts are welcome.