The stock heads are good for 600rwhp. They flow really well. I think the "feel" you're looking for won't be found in such a solid setup like a 1LE.. there isn't a fly by the seat of your pants feeling of rocketing forward because of all the stiff suspension - you're not bouncing around like how much faster I felt in my Mustang, or how I'd assume a Caddy to act. That's just my guess anyways.