erratic

my late 99 7.3 has some strange idle at random times. Fires right up runs fine cold/hot. But sometimes after driving for a little bit if you sit for a little while weather you are in gear or in park, the idle with bounce. Its not dramatic but you can see it on the tach, it will jump up and down...

Intermittent wipers are causing my speedo to act erratic. When I use speed 2 thru 4 on my wipers the speedo jumps. I have an 09 f350 single rear wheel with only 38k miles. I am assuming it's wire related but would greatly appreciate some help. thanks