Missing Under Power

I have a 99 Ford Explorer 4.0. After I tuned it up, Changed plugs and wires, it now has a miss under power. I have checked all wires ect. Anyone have any ideas. It was not missing before tuneup. Thanks

Not unheard of to have a bad plug, plus, common problem is cracked plug insulator. Could been that way when bought, or done when installing. easy to do. Unless a vaccum line knocked off etc. unsure of anything else it could be.

Thanks for your reply, I found the problem, it was the Bosch plugs!!
There was two bad plugs out of six. Not a very good average. I installed autolite and now everthing is ok. I talked to a local mechanic and was informed there is many problems with Bosch plugs.