Exhaust ?

I want to squeze a few more hp and tq out from the exhaust. The factory exhaust is pretty big, So would a highflow cat and a turbo muffler get me any gains. Make me a little bit happier with this car?

YES! Anytime you can ease the flow of air, into or out of, an engine, it will produce more power. Less drag.

To prove this to yourself... Go to your local kwik mart and take a coffee stir stick. Blow as hard as you can untill out of breath. Then, try the same thing with a regular soda straw. Not much effort the second time huh?!
The same principle applies. A larger inside diameter with eased bends, will increase airflow out on the engine. Yes, the K&N air intake system works. But not as well without a free-flowing exhaust.

When the engine's cylinder head is said to be "ported", this means the machinist boared out the passageways, increasing the airflow.

If you're old enough to remember side pipes for the Camaro and Trans Am, these were more for power than for looks. (Though they look pretty cool)
the main purpose of side pipes was to eliminate the over the axle bends and increase airflow/horsepower.