I may be a bit sensitive but the fumes were too much for me. I had the Pypes X with no cats and I only lasted a week. I also have a Evo. tune & JLT II. I was getting headaches and my eyes were burning a bit. Also my throat was scratchy. I have a little girl and 10 hp was just not worth it to me. Funny thing is I had a 93 5.0 without cats and it never bothered me. Just my 2 cents.