I can't decide.

None that you'll notice. If you want more power you're really going to need to go with a true X pipe like Dr. Gas or Bassani or something. Don't expect huge gains from what you're planning on.. especially if you plan to leave the cats on (high flow or not.)

you will see some gain but it also depends on what tone you want if you want the old muscle car tone then stick with the H but in reality you should go for the O/R prochamber that itself acts as a muffler

I don't think you will feal anything with on the mufflers. I went to a whole borla catback and did not feel much. probaly there but noting I really noticably felt.

I felt the x-pipe alot though. I have an O/R pipe though can't comment on the catted pipe. most of the gain you would get would be from the midpipe on this approach. I would get a different one than the mac but that is me. from what I have read DR. gas is the kind of the HP. the flowtech looks very similar as well. I went vrs becasue I wanted stainless.