Regular or Premium?

A lot of people would say get premium for your cars engine so it will run and perform smoother and better. Like hell. I bought a full tank of premium gas for the Mustang and I have to say I am glad my car doesn't like the rich stuff. I have lost some compression and some power switching to the higher grade. It runs quieter and alot smoother, but its lacking alot of the low end -umph- and high end -grunt- I am used to.

Its strage, it feels like the car is bloated!