Determining injector size without knowing where the injectors came from?

[N0DIH]

I have a 99 K2500 Burb with the 7400/L29/454, tuned by Jesse (love the tune, great power). But the previous owners (a corp vehicle) must have installed larger injectors, I suspect to run a higher % of ethanol fuel, if not E85, but I can't confirm.

It always runs rich, unless I run a nice dose of E85 (40% or so) and BLM/LTFT come down to 0%. With pure gas (no Ethanol) the LTFT runs -18.0% stable. Not 18.1%, not 17.9%. Precisely 18.0%. If a fuel leak like a leaky FPR, it would NOT be that precise. And fuel pressure is dead on GM specs, and does not bleed or leak down when not running.

So, do I recalc the injector size for 18% larger to LTFT come in line?

I am just tired of having it run rich (yes, the O2's are new, old ones were really ok, FPR is good, new unrestricted air filter, new plugs, good wires, good cap/rotor, vapor canister ok, etc, yeah, I have gone through it all).

What would the best way to figure it out with a mail order tuner?

Sheesh, I am ready to descreen the MAF just to screw up the A/F to lean it out!

Thanks!!

[RUTAN TA]

Is there a pt# on the injector anywhere?

[N0DIH]

I can only see #2 and only about 30% of it, and I can't turn it hardly at all, and I can't see one. If it is there, I would have to remove it to find it. And on the L29 454, that requires removing the upper intake plenum. Not exactly a fun job.

Which is why I would prefer to figure it out another way if possible.