wiper blade inserts

I've replaced the wiper blade inserts. But if I go faster than about 50 miles, the wiper blade on the drivers side doesn't clean very well anymore. I already swapped the wipers, but then I get a dead spot on the passengers side at low speeds as well (sorry if this isn't clear :banghead: ) It seems the drives side need more pressure ? How can I fix this?
Also the driver side wiper has some kind of spoiler on it. Why is that only on 1 wiper?

Make sure all the joints on your wiper blade move free and easy so that there are no binds. If all is well, then you may need to bend the wiper arm slightly, just enough so that the blade makes good contact with the windshield. Someone must have replaced the whole blade on the drivers side at one time, thus the spoiler.

You will also want to check the joint at the base of the wiper arm, make sure it moves without any binding.

I checked it and bend the arm a bit, but to no avail.
Could the spoiler be the culprit (is this an original option for the Park Avenue?) I noticed that while the wiper works at lower speeds, above ±60 miles or with heavy wind the wiper actually hovers above the windshield.

The spring tension in the wiper arm may be weak, if that's the case, you'll need the entire arm. The "spoiler" is designed to catch the wind and hold the blade to the windshield.