Your tuner can do this for you. He can mod the ecm to accept the lbz regulator. You're thinking to hard about the process.
Head gaskets...check
45% SAC...check
Having Tony Tune your ecm...check
Everything that you would need to do with a V2 to your ecm Tony can do with his V2 to your ecm.
You CAN run a stock tune with 45% injectors. What we are saying is that IF YOU TOW the 45s will be hot and you will really have to watch egt.
When you have enough money...get your truck tuned. If you the money to get an ecm tuned by mail Tony can do that. Do that while your doing you HG and injectors.
If you can get an autocal, financially, do that instead of the tuned ecm. The reason why you want an autocal is because if you want Tony to make adjustments tot the tuning you can send him files of your truck running and he can tell where the changes need to take place.
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