I have had something similar happen with my '84 on several occasions.
Plugwire connections at #1 and #3 plugs get more corrosion than
connections at #2 and #4.  Until I started using dielectric grease on
the connections, I have had failures within 6 months of new plugs and
wires.

John

On Mon, 2011-09-26 at 17:26 -0400, TJ Hemrick wrote:
> I'm going to throw this out there as I'm still having some trouble and
> perplexing trouble at that.  I've been having some problems getting the van
> up to speed and holding speed on the highway.  it starts, runs, accelerates
> fine.  It's a little slow after 50 but right at 60 mph (4k), the engine just
> stops pulling.  If I give it any more gas, she just winds down.  I have to
> back pedal to get it up there and keep it there.  It's a VERY fine sweet
> spot and I have NO power at that speed.  People are blowing by me like I'm
> going backwards.
> Here's the crazy part, if I floor it, it bogs down and will ONLY do 45 mph
> and it has a very slight sputter to it.
>
> Here's the scoop: 87 GL, 2WD, Auto, stock 2.1, I COMPLETELY cleaned the fuel
> tank out for a fresh set of gaskets about 6 months ago, new fuel filter, new
> fuel pump, new fuel lines from bow to stern (dumped the firewall fitting),
> new FI clamps and hoses on the injectors, and has been running well (aside
> from marginal gas mileage).
>
> I've been through a few tanks of gas and a bottle of water remover so that's
> a non issue.--NO CHANGE.
> I swapped AFM's since it's quick, easy, and I have a few spares. --NO
> CHANGE.
> I swapped Air filters (for the same reason as above). --NO CHANGE.
>
> I've pretty much given up on a fuel flow or air flow issue as it's at the
> EXACT same speed/RPM range EVERY time that's plaguing me with the slowdown
> and it's ONLY when I dump her to the floor that it goes into the speed
> DECREASE.  It's so counter intuitive to back off the pedal when you're
> trying to pick up speed.  Especially when just one or two millimeters too
> much and now you're slowing down due to throttle position and that semi is
> right at your back door and closing fast!
>
> I'm going to check the cap and rotor but anyone have any other thoughts or
> heard/seen this?
> It's just so strange that it starts and runs fine at all other points.  I
> guess I shouldn't completely discount a fuel issue but it's not like the new
> pump is cavitating ONLY at that speed and every time ONLY at that speed.  I
> guess it could be a total fuel volume issue but how could it be, again, only
> at that almost exact same point each and every time?  Seems too specific for
> fuel.  Electronics are the only things I know of that can be so repetitive
> and exact.  That keeps putting me back at ignition.
>
> Thanks,
>
> TJ
>
> Yes, I have spare ECM's and AFM's so playing swaptronics is not a problem.