My 4Runner runs like crap on the freeway

[Sik4Runners]

I have an 86 4Runner with the 22RE and automatic with overdrive transmission. I have a 4:30 gear ratio on 33" tires and 15x8 rims. When i drive my truck on the freeway and get upto 65 or 70 the overdrive kicks in and the truck usually cruises smooth. But lately it has started to slow down to 52 and will cruise at that on OD but it will not keep a constant speed any faster than that unless I take it out of overdrive. If i try to cruise at 65 or 70 out of overdrive, my truck revs at 3700 RPMs. I don't want to run it that hard. The truck acts to me like it is not getting an efficient spark or enough fuel. I have done a full tune up, oil change, new coil, New fuel pressure damper, and adjusted the timing. Nothing works. Can you guys help ? Another question......what the hell is that thing on top of the ignition coil? Is it the igniter? Do those go bad?

[Sik4Runners]

Here is a picture of my coil.