Intermittent miss

2000 Ford e 150 conversion van. 4.6 triton, 120,000 mi. I recently purchased this van that appears to have been well maintained. It ran great until I washed the engine. Then I learned you don't wash the Tritons because of spark plugs mounted like early hemi's! It missed badly & didn't "dry out" The plugs were replaced-old ones look as tho they had been replaced not too long back. Started replacing coil boots, then one at a time the coils. After two and still a miss-not as bad- I had all 8 coils replaced, including the earlier 2. It now ran like it did when I bought it. 2000 miles later, now in TX. (1200 miles from home) it started missing one damp cool morning. At idle I can not feel miss. Put in gear at idle & I can feel it. When driving, miss is intermittent. Under hard throttle it does not seem to miss, but with soft throttle and moderate pull-like in overdrive at 50 on slight hill- it will miss.
I plan to replace the coils, 2 at a time using the new ones that I had replaced & see if that will fix. I Understand it is not easy on van, so would like your opinion before I start. MAP sensor? I read some of the articles in the faq & wondered if it would be easier to try that first. During routine maint I replaced the air filter before leaving on trip alto the old one was not very dirty.
Thanks, Frank