After I got the B&B triflow on I noticed a quiet hiss/air leaking from the rear of the car, maybe it'd always been there and I just never noticed it. I only hear it when I'm excellerating and at low rpms, once I get around 3K rpms the sound is covered up by the exhaust note.

ONce I let off the gas the sound goes away. I thought it was an exhaust leak, but my dad rode it in and thought it was the fuel pump hiss. We've tightened up the exhaust pipes and the sound went away-sort of, the first time. The second time we tightened it, the sound remains the same. Anyone else notice this?

 

You should be able to hear the fuel pump hiss all the time, even with the car just sitting there.