Hey there I have researched this for the past couple days and no luck. I installed a O/R H on my car to a Steeda catback and my car has a exhaust poping noise from 2k to about 3.5k rpm range and it goes smooth again. I have my spark plugs gapped to .035 and its still doing it. I have a 2.75 upper with O/R h, Steeda CB and JLT Ram intake. The car runs great and idles great just pops really loud threw that rpm range at WOT. Any help will be great, I have a set of flowmasters I want to put on but they sound horrible with the popping!