Exhaust could be getting clogged up which effects power at highway speeds, back pressure increase so new fuel can't be pulled in.
Vacuum gauge can tell if that is happening.
Dirty Fuel filter also can limit fuel replacement at high speeds so no power.
Replacing fuel filter on "new" old vehicle is always a good idea.
Google: autozone 1988 ranger vacuum
Autozone has a good repair site with vacuum and wiring diagrams.
Look for a vacuum diagram for a 2.0 or 2.3 that didn't come with smog pump.
The smog system on some engines helped to prevent "pinging", so after removal if you start to get 'pinging" on acceleration you may have to reset the spark timing or run higher octane gas.
EGR system does not "take" power, it helps keep the cylinders cooler under load, this lowers the emissions, but also helps prevent "pinging"
Last edited by RonD; 01-08-2014 at 11:05 AM.