Cruz

I've had the UT Ypipe on for about a month now and I'm experiencing short spurts of raspiness in the tone of the exhaust at certain rpms. I thought it might be something rattling underneath like the heatshield but now I know for sure it's coming from the exhaust. Other than having the Ztube & UT airfilter I'm pretty much stock. My question is...Would this sound be caused from having a free flowing Ypipe going into the more restrictive stock mid pipe & exhaust?

Thanx