Driving my 98 s10 4.3L then all of a sudden my truck seems to be losing horsepower going up hills and the exhaust note changes! Also I believe my truck has a hole in the exhaust and the cat converter rattles. The truck is louder than normal an makes a whistling sound when I get on the acclerator. And when I get on the gas seems like the truck just won't go like somthings holding it back? Could backpressure cause the truck to loose power? Just happened after I got gas and started through the gears engine has no rattles or knocks about it an revs freely?