I run a Holley HP system on my car and love it. No issues at all. 2nd Holley EFI system that I've installed and I'm able to tune it myself. That being said, I would keep the Pro-M if I were you. IMO, Mass Air>Speed Density. It's Pro-M's single greatest advantage over Holley.
I have zero experience with the Pro-M but there is nothing that I've seen or read that makes me think the Pro-M can't do everything a Holley can. Money is the main reason I chose Holley but you already have the Pro-M so why take the $$$ loss?
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