l would like to go faster on the freeway with my pt cruiser cause it does'nt seems to pick up power

There are chips available for the computer.

well Chrysler does make a turbo for the pt cruiser, and with performance exhaust and intake that would help a lot.

Like the other before me said, there are chips available, aswell chrysler does make a turbo for it.
Flowmaster does also make a full exaust system for the PT Crusier.
And as the PT is based on the dodge neon, any part that should fit a neon, ie- exaust manifolds, cold air intakes and the such, should beable to fit the PT.

The pt cruiser really is not meant to be a powerful car. Even the turbo version is still slow. You could put a computer chip in it and get more top speed but make sure your tire are speed rated to the new speed your driving. The turbo is the best way to get more power out of a non turbo engine but it will cost alot. And also will void your warranty. If you are going to up-grade your speed you should also upgrade your brakes.