Haha i had a mid section replaced too and cost me 300 with labour
I say have it checked out.. if its nothing major that could snap or go wrong anytime soon just suck it up, or if you have the money just buy a whole new system. But guess if you were going to get a new system soon you wouldnt have had original part changed..
P.S one evening i started up the car and too had some blowing noise from underneath.. had a slight worry thinking it might go wrong again, picked up my mates, had a good run on the way to london, started it up after clubbing the noise gone away.. and now nothing changed for a week.