I knw this is a old thread but maybe someone out runs into a similar problem and can use this. I ran I to this same problem on my parents Vortec 4.3 blazer which is basically the same thing. And you knw who was to blame for cylinders not running the darn fuel injection spider system. When I swap these out I wish you could see how badly burnt the end where my god!! Luckily I found them cheap on eBay and I had a friend give me some very helpful advise. He ran compression tests we uncapped the engine and we could not find jack, 96-I believe 2000 uses the same spider system if u haven't already fixed this I'd give a shot a new fuel system will even ensure ur gas mileage is up to date.
I'm doing the same here rebuilding entire 5.7 with a few lil goodies for my 99 Tahoe but this time it's getting everything new including the spider system trust me its a pain a change once the motors in the car why go threw all that to save $100. Hope that helps u guys a out a bit. Laters