[83GMCK2500]

x2 on the 5-oh injectors, great choice. I've witnessed two sets of them fix rough running/starting 454s. I have a set waiting to go in mine. Also a 0411 w/Blackbear tune. Just need the time.

You may have solved any fuel issues you had and now something else is showing, the distributors on these things will notoriously wear out and cause the timing to jump around. There is a procedure for setting them, I'd have to look it up if you're not already familiar.