[twobjshelbys]

But before you go diving into the DFI hardware, that 8-stack is incredibly finicky. Acquire one of the vacuum gauges and go through the throttle body adjustments. You have to do an 8-way iterative adjustment that will probably at least once lead to an unsolvable solution in that you can't get one side to converge with the other. You'll have to adjust the throttle cable in the turnbuckle to center it and start over... I think I have the procedure document still around somewhere.

From your description of a few plugs fouled to all I'd start with this adjustment first. If the vacuum device shows the same on all 8 cyls you're ok. Then you go to try to figure out why the afr is wrong. Adjusting the blades to get them all pointed the same angle at the same time will also mess with afr. It's a tedious iterative process.

It's also really finicky since the cam in the 427IR is really lopey and getting a good vacuum registration on the tool at idle is really hard. I raised my idle to 1000rpm...