HELP with my 5.0 VAN!

I just got a ford 1992 E-150 5.0 conversion van for free, and its real nice.
but the thing wont idle for shi*. i dont know much about the motor thats in it, heres what i do know.
intake manifold has a dual butterfly TB that faces the front of the engine
there is a sticker under the hood that says "the idel speed, idle air , and timeing are not adjustable"
wires go dirictly into the distro and there is not a "modual" on it like there is on mustangs

i changed the plugs and wires and still no luck, it takes a lot of cranking and "poping sounds" to even get it to run. i also saw a few flames and small backfires in the intake manifold while my buddy tried to start it.
even though it says "timeing is not adjustable" i loosened the distro bolt and it does advance and retard the timeing but that does not help it run better. it runs ok if you hold it at part throttle, and sounds strong when you rev it up.
(its not missing or skipping)
there is also a small crack in the exhaust manifold that blows some smoke if you rev it hard but its not that large. im gonna replace the manifold of course but i wouldnt think thats the entire problem.
does anyone know the the differences between this engine and the ones in our mustangs.
i pulled the new plugs out about an hour after i installed them, and they are dry, black, and have a good amount of carbon on them. can i use a hand held code scanner on this motor? the type from the parts store?

oh yeh i dont see a MAF anywhere in the intake system.....
any suggestions?
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yeh i thought of that too all the lines are run inside wire loom. also, the fact that it is a van makes it pretty hard to see the whole motor.
with the cracked exhaust manifold and flames backfireing into the intake maifold i am reluctant to spray starting fluid on the vacum connections, no what i mean?