2003 Hyundai Tiburon • 120 miles

My car is a GT 2.7L 6-speed and it doesn't feel like its pushing full horsepower. Also, when it reaches normal temp it idles a bit rough. Like a slight shudder you can see looking at the engine and feel sitting in it. But the rpms don't move. When driving, I take my foot off the gas to coast and when I depress the gas again (not flooring it : ) ) the car jolts. It feels like when you catch a gear hard when shifting. There is no check engine light and no codes.
What I've done so far: new plugs (ngk iridiums), wires, TPS, fuel filter, air intake hose, air filter, cleaned the throttle body, MAF sensor, and IAC valve. I went to Valvoline and had the full fuel system cleaning and just got an oil change. This is driving me crazy! Any help is incredibly appreciated.
November 10, 2012.

Should say 120k miles. Sorry!

Nov 10, 2012.
I am giving you a walk through diagnostic for your situation. Just use the link below to get to it;