CPI: rebuilt vs new?

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Anyone have advice on wether it is better to buy a rebuilt CPI unit or go for an AC Delco unit???

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Ive had bad luck with CPI units...im sure alot of people on this form can relate...
I brought my truck to GM, and they wasted a bunch of my time and money suggesting problems...and finally blamed my misfiring on my CPI unit. I even purchased an EGR valve for nothing because of their stupidity (still have it if anyone needs one ;-} ).
I bought a new CPI unit off ebay, and stuck it in... seemed good, but started misfiring again. I sent it back, the guy sent me a replacement...and same thing! MISFIRING. No fuel getting to cylinder #4 (infortunately never checked which cylinder was the problem last time).
Now im out 250 bucks, and want to take no more risks with CPI units, so i want to know what i should buy, ?rebuilt or new?
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Oh, and instead of making a new post, i have another related question: does anyone know how the CPI distributes fuel...does it know when to discharge?? it only has two wires going to it!! OR do the poppet vavles deliver fuel when there is vaccuum present (ie on the intake stroke).

You will ususally have to replace the plugs after you do the CPI replacement.

I had to to seeing the plugs will be carboned up on one side and lean on the other side when the injector was busted.

I did all the cpi work here:

http://www.s10forum.com/forum/showthread.php?t=113559&highlight=CPI+replacement

Man, it ran a little rough after the replacement, but new plugs set it back to its beautiful self.