I've got the exact same setup in my car (but i DO have a cat) and i have the EXACT same problem with loudness as well. Unfortunately the 4AGZE is renowned for being unbearably loud and I've put up with it too long as well! The only suggestion i can think of would be to run double resonators, and maybe a silencer? But I guess if you want real results, a dampening resonator would be the go.