[blykins]

You will make it infinitely louder if you keep reducing the amount of "stuff" that's inside of those pipes. It's not really the packing anyway, it's the ID of that hole going through the muffler.

However, restrictive sidepipes have been shown to take 100hp, so what do you do, right?

Sidepipe mufflers would be the easiest route probably.

I wouldn't swap the intake as a smaller inch motor wouldn't most likely gain a tad bit of power on the very top end, but lose a lot of low end and mid range power.

If I were going to get into the heads, I would swap brands altogether. The Procomp stuff flows like factory iron...very restrictive. You could pick up 50-75hp by going to a nice head like an AFR or Brodix.