A header/presilencer from RB or control arm bushings front/rear and rear strut tower bar for my 90 NA? I have a straight pipe for the exhaust already, and the bushings aren't in bad shape currently(although they are the stock type). I have a front tower bar, RB sway bars and RB end-links in the rear. I can hear creaking coming from the frame now that some of the other things have been firmed up, that's why I'm looking at rear strut tower bars. Anyone? I'm slightly leaning toward the header, but if it's louder with an HKS cat-back than just a straight pipe, that will count against it. Sorry for the long post(i always explain things too much)

 

I will be much luder. I have this setup. My cat back started on the stock manifold with a down pipe and hi flo cat. Now it is the RB header and presilencer. LOUD!

The car would be more fun to drive if you got the bushings.
You have already improved breating. finish your suspension mod.