brand new, your engine only put out 115 hp, according to the ford specs. not a lot to start with really. even loosing the emission stuff, your probably only gaining 3-5 hp... probably not enough for you to notice really. also, if you have the auto tranny, that sucks away a few ponies as well.
i had a similar problem and found that the intake manifold was nearly plugged completely with gunk. try taking it off and cleaning it really good and put new gaskets on it. that helped mine lots. also had a rear main seal leaking as well as the oil pan gasket. had the engine pulled and every gasket, seal, etc. i could find replaced with Felpro gaskets. also got a new high volume oil pump put in because it would be one less thing to go bad in the future.
also, have you changed out your valve seals? they get old, harden and let lots of oil get by.
now, did you check either the axle tag or your door code tag to see what axle ratio you have? if it's the 3.45 ratio gears, that will be a big part of your truck feeling wimpy. replaced my 3.45's with 4.56's and couldn't be happier. also had a detroit locker put in the rear while it was apart for the gears. excellent combination even with only 31in tires.
those are some of the things you can check out for your truck. use the tech library here:
http://www.therangerstation.com/tech_library/index.php and you'll find a wealth of info for your ranger.
good luck, and...
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