I put a bigger wiper from my old tib on my GFs car about a week ago and 3 days ago the wipers started to slow down. Now they go extremely slow and they bounce over the windshield. Do you guys think it overloaded the motor?

Did you check to make sure they're torqued down the proper amount? If you did it too much they will be to close to the windshield and have too much friction, if you didn't do it enough the nut will be spinning and the wiper won't really go anywhere.

The wiper linkage probably needs to be replaced. I had to replace mine becasue the wipers were moving slowly. One of the pivots was so stiff you couldn't even move it by hand.

I don't think putter a wiper blade that is a little longer is going to have any effect like that. I think it is just a coincidence that you noticed it around the same time.

I had the 22" and 20" wiper pair blade installed (I hope the figure is the correct), the max for RD1 front windscreen, in fact the passenger wiper blade is over the windscreen edge (RHD here). Running that wiper blade setup for more than 2 years, doesn't give my wiper motor any issue (touch wood), but I did change my wiper arm links . I'm using smaller size wiper blade now (20" and 18").

I believe longer wiper blade does give much more working pressure to the wiper motor and wiper arm links, especially most of you guys have winter time. And it won't give you much bigger view. Perhaps sticks with stock size will be better.

Just because links are stiff does not mean they are stuffed. You can get at the linkage beneath the cowl (on most cars) at the base of the windshield. Either slowly take the links apart piece by piece and grease them up, or get one of those oiling tubes with the pinpoint "needle" to inject lubricant right into the linkage. After moving them around a few times by hand, they should be just like new.