Exhaust proximity to fuel lines etc
so you went up from 2.5" to 3" inch exhaust, which moved the exhaust 0.25" closer to the fuel line/pump...correct?
and i presume we are talking about the rear section of the car, roughly by axle
at that point there is still some heat left in the exhaust, but nothing close to the under hood temps
honestly, i wouldnt worry about it