I have installed a new motor and better-used linkage. The wipers move slow. They speed up when the windshield is wet. They seem to have no power.

Have a good look at the wiring. Also the ground and fuse to see if they're corroded. My wipers got a whole lot better after refurbishing the fuse box.

X2... I'd start with that too..plus it's free...just takes a little of your time. At least then you'd know that all of your electrical contacts are good and can rule them out if there was an underlying issue besides that.

I resolved my problem with the slow wipers. The relay connectors were corroded. I clean the connectors and ground a metal fingernail file to the with of the connecter and cleaned the connectors in the fuse box then I put some dielectric grease on the connectors. The wipers are now working properly. I was so impressed on how the wipers work I clean every fuse and relay in the fuse box. Thanks for the advice.

I have the same issue. Slow but speeds up a little when wet. Now the wiper auto park is acting weird. It stops at different positions instead of at the base of the windshield but only when I push the wiper arm tab (which has it do 2 swipes). It has an intermittent wiper function and that works well and wipers park correctly. It's only when I push the wiper tab on the stalk. .
Cruiser recommended adding another ground to the wiper motor. I did that a couple of weeks ago but it didn't fix the problem. I have good ground and 12V at the motor.

The motor is new but I'm guessing that's my problem.

My problem was the fuse terminal was corroded. I took a fingernail file, cleaned the terminals, and used dielectric grease to help stop any more corrosion. This solved my problem. I cleaned every fused in my fuse box this way.

It turned out to be the intermittent module under the dash on mine. I stuck another one in there and I'm back to normal..