Hey guys I got a question here. nEed to know if the h22a1 or h22a4s all use hte same headgasket as the h22a. because I have a H22a and am trying to lower my compression w/ a thicker headgasket for boost. I need to know which headgasket I can use and where to get it from. I hear that H22a is closed deck and the others (usdm h22s) are open deck. I just want to know if the head gaskets are all the same.