GAMI injectors for Lycoming engines

That depends on how well balanced the cylinders are with the present injectors. Usually, Lycomings are rather terrible as they come from the factory. Have you completed the GAMI lean test?

If you do the lean test (and it needs to be done to exactly their spec) and upload it to SavvyAnalysis, you can send the link to GAMI and they will tell you.

My experience across four TIO-540s is that the spread was so good and close that GAMInjectors were not necessary, and GAMI was quick to tell me so, so they are a decent and honest company to deal with.

My AFM actually specifies LoP operation (on a 1973 airframe) so maybe they put in special efforts to balance the injectors. Having said that, I have engines from all provenances, so it must be a general TIO540 thing.

Keep in mind that the injectors are only a part of the equation. You need good mags, spark plugs (Tempest), ignition leads etc.
My Champion fine-wire spark plugs tested good on the bench, but the difference after switching to Tempest was dramatic.

What I find remarkable is that with factory fit everything, nothing special, I can just pull the levers to the exact book figures for 65% LoP and it just performs exactly to book – no fuss, no vibration, it just does it.

The TCM IO550 and 520 is a different story due to the induction system. They run very well LOP but most need a bit of work. The top-down spider induction system is much better than the old log-branch with rubber couplings and uneven fuel distribution due to carryover.
Anyway, if you do the GAMItest and you don’t need GAMIjectors, they will tell you and not try to sell them. If you need them, they will help you set up the engine by swapping injectors when needed.