so are the reviews on zzp.com full of crap? like this one
"These headers are truly amazing. Last fall my car was wideband tuned with a gen v, xp cam, and tog headers, and all the supporting mods. We reached 18* of timing advance at WOT with a 2.7" pulley, hitting a max of 13psi. Over the winter I installed the ZZP headers and in the spring I noticed my boost had dropped to 11.5psi with the 2.7 pulley. I threw a 2.55" pulley on and to my surprise I couldn't see any consistent knock anywhere. So the ZZP headers let me drop from a 2.7" pulley to a 2.55" with 0 knock and thats comparing them to TOGS. Currently the car is running around the 14psi range depending on weather."