Thread: Identical l67 engines, very different power levels. Why?

I should have clarified this part. I only meant small mods that could support later mods, in the same fashion as removing the u-bend. No real power gain by itself, but it helps with later mods. I don't know if there will be any similar things to do while the top is off, and I don't want to have to take it apart twice.
I've read through the "safely modding" thread and learned quite a bit. That thread stopped me from buying a pulley right away. I'll do all the supporting things first + a tune (maybe) and see what I've got. If I still want more, then I'll consider going further. I read in one of the threads that you can get into the 13s at sea level without a pulley. Don't know if it's true or not, but it goes to show there's a lot pf power already in these engines without really adding anything to them.