Lowering compression absolutely can increase power and performance at all RPM depending on what the setup is, every setup is different. There is a reason the supercharged Coyotes are still kinda peaky while the Terminator and GT500 feel like they have big blocks.
But this guy is smoking crack. Also you can buy a 700hp Roush for like $38k with a full 3/36 warranty so...
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.