19s will support roughly 300 horspower at 85% efficiency.
I'm only 17 so feel free to contradict me on anything I say and I'm open for learning... I think 30's are large for his combo, yes, but not in a bad way. I personally don't think they're hurting him.
With a MAF car your mass air reads how much air is coming into the engine. So with a factory mass air meter and 19lbs. injectors, the air coming through the meter tells the ECU/injector harness how much time to take between each injector pulse. If my understanding is correct the more air that's coming in, the shorter the time is between pulses. Say you're going to stick with 19s and install them on a 347 with a set of 185cc heads with matching cam and intake. You're probably going to be making alot more than 300hp which is in the ballpark of a set of 19lbs. injectors 85% duty cycle. Pretend you're combo should produce around 375hp. The air that this engine is going to flow is enough to decrease the time inbetween pulses to the point that the injectors will stay open constantly. I think that point is a little above 325hp.This is not good. LOL. I've also read that they can fail from overheating due to this.
A meter programmed for 19lbs. injectors will have a set pulse width that varies with amount of air coming into the engine. If I were to put a set of 24lbs. injectors in my combo with a stock mass air meter it would run like crap because the ecu wouldn't adjust the pulse width to accomodate for the larger injectors. For the most part it would run overly rich. Now say I matched a set of 30lbs. injectors with a mass air meter programmed for 30lbs. injectors. The meter would adjust the pulse width to accomodate for this.
If I had a set amount of air coming into a built 347 with a set of 24lbs. inj. at 5000rpm and a copy of the same engine with the same amount of air coming into it at 5000rpm, although this one had 30lbs. injectors then they would pump the same amount of fuel in for that amount of air due to different pulse widths as long as the smaller set of injectors is NOT at its max.