I've got the old exhaust and over the last three years they have got noticable louder and deeper

I also have the big 4040 K&N filters and Tune boy and also cycle barn in Seattle put alluminum 1/8 thick behind the filters ,they said they did that so the filters won't suck up the heat from the engine and will breath in more cool air to perform better, it was one or there tricks they did and they said they proved it on Dyno. So maybe I'll see the 200hp but could still live with under

But those headers are proven to be even better then my Jardines header and will hook up to my Jardines,I will buy them unless the results are not worth it.