Based on what I've seen, the DC headers make 1-3 whp for the H22 without the 2.5 inch collector. I've been looking for some info on what kind of power can be gained by modifying the collector to 2.5 inches, but can't find anything. Anyone have any info on this? I don't mind spending money for a RMF header, but have heard that they aren't worth having unless I plan on going for big power in my car. Apparently the gains aren't as impressive with a mildly upgraded engine....right? Thanks.