For some reason whenever I give my car some gas it gives off a whistleing noise, and when I get off the gas it goes away. I am guessing it has something to do with the exhaust ( I just got a new muffler and tailpipe since the last one got ripped off in the woods, and I blew everything out of the cat cuz it was broken up, didnt have enough money for the whole new system at the time. But yesterday I was going up a decent sized paved hill and when i gave it gas it sounded like my car was almost about to stall out like it had no power to make it up the hill. Any ideas what this could be? thanks alot for the help.