Blown Rear Silencer - link to probs??

My rear silencer (525i M20) has had a hole above the two inlet pipes that has progressively got larger. Sounds great :D !! but I have noticed that my fuel consumption is going up slowly, and also the gearbox is taking longer to change into 4th gear. It now changes at around 65-70kph where as before it routinely changed at 60kph. Would this be related to the rear silencer, or is my gearbox on the way out??
Thanks
Garry - Perth w.a

I dont think your muffler has anythign to do with it.

I bet you're mashing the throttle harder 'cause you're driving to the exhaust noise instead of the engine sound.