Consequences of famous "free" mods

[Ziggymidget5]

I'm sure that most of you have heard about the free mods for preludes, and if not, here is the site Brady's Webpage. I could ask a million question, but I have a few in particular. First, will any of these mods have harmful effects on the engine? Second, will the fuel pressure regulator mod significantly lower gas mileage or make things to rich or mess up the catalytic converter in any way? The butterfly mod apparently loses lower end HP and torque, but I saw a dyno graph where it actually stayed the same, but made 5 or so HP up top. This could have been because the extra ports weren't opening as they should, but still, it should have showed bottom end losses. Does leaving all the runners always open really lose power? And does advancing the timing 1-5 degrees really have any negative effects, either top end performance, or harmful effects? I know that if it pings you have to retard it until it stops. Any input is appreciated, and feel free to add on, and answer whichever questions you can, I hope this helps other people too. Check out the rest of Brady's site, especially you H23ers out there, it's really good and keeps my hopes up.