'95 Astro - Engine misfiring

Like everyone I'm trying to find a fix to a problem I've isolated ...

1995 Astro
4.3 Vortec "W" Engine
160,000 miles

New plugs, new wires, new distributor, new rotor, new EGR, new fuel filter, new PCV and new air filter.

Engine idles rough and while driving at speed and accelleration, it hestitates.

Pulling the spark plug wires off the distributor results in the following:
For cylinders 1, 3, 5 - additional misfiring
For cylinders 2, 4, 6 - absolutely no change in how it runs

Pulled the spark plugs: 1, 3, 5 - fine; 2, 4, 6 - carboned up

Cleaned the plugs from 2, 4, 6 - no change in engine idle. Took the plug from 3 and switched it with 6, same results.

History - Check Engine light: EGR Code = EGR replaced
Used to get 20 mpg, dropped to @11 mpg before EGR and tune-up
Now its stretching it to get 15 mpg

Any thoughts from the group would be greatly appreciated. Thank you.

Greg

Fuel injection spider would be my guess....

Thanks for the reply.

I'm getting desparate trying to figure this out.

Anyone have any additonal ideas?

Thanks again.

Yeah sounds like the CPI. Check to see if there is gas in your oil.

Thanks again for the replies to my question. I appreciate it.

One more question please ...

Since this repair seems to be WAY out of my league, what am I looking at for parts and labor to get it repaired? Ball park estimate is fine.

Or any other suggestions.

Greg

Well you can get the part off ebay for roughly $250. It took me most of a morning to replace. So figure 4-6 hours at your local rates....

But it's not the hard to do. I actually did it twice in one day. I messed up seating one of the poppets.

You have to remove the upper intake manifold, just ten small bolts, and remove and replace the injector unit. The hardest part was getting the upper manifold out. Had to slightly bend the AC line to get it up and out.

Thanks again!

I've been looking over my repair manual and thinking about giving it a try.