are the injectors 12 to 14 ohms impedance?

are you sure of their lb/hr or cc/min capacity
or going by advertising?
Who has told you what about them?

Any chance during the injector install
that ignition wires to cylinders 6 and 8 got reversed
or placed too close to one another?
That is a common backfire producer and the 'correct' placement of the ign wires to 6 and 8 looks nothing like 'common sense' would tell you to do.

 

With the injectors, fueling is based on pulse width- which basically means time. The factory programming goes up to 13ms at wot (or myfactory programming did). Dave goes way bigger. If you put too big an injector in without programming, the pcm will struggle to get the trims right at idle, and wot is going to be way off. With the m1 flash and 25lber's, you're probably looking at 10.5-12:1 wot, and your idle trims are probably in the -25% range. You can easily add a bunch of hp with a tune. I can post some datalog graphs of mine if you want. I'm down to ~5.5 secs. 0-60 with a full toolbox and a full tank of gas. 12.4 wot had me at 5.8 and i actually logged a 5.2 yesterday at 12.8 (for the most part). 12.2 had me up around 6.

 

Always able to getmy syncin the ballpark so its good enough to drive.Thenuse asnap on scan tool(borrow from parts guy)to set itto 0-1deg+(usually off 4-5deg).

Do you have a flash for the bigger injectors & cam?
Id check the impedence of those injectors as Hank suggests
Those are GM LS1 24lb arent they? Most gm injectors are too low or too high an impedence for us to use. Not sure if a flash can account for the different impedance or not. Checking racetronix.com (gm fuel part site) they list either 12.2ohm or 15.9-16.2 ohm injectors.
Anything hi impedence I use to run was between 14.0-14.4ohm. Matched set were always within .1 ohm of each other and unmatched usually .2-.3 variance. My FAST 65lb are low imped. andall are bang on 2.5ohm(stand alone eng/mngmnt).