I don't know if this is what you are experiencing but the newer Rangers don't use much engine braking when you let up on the accelerator pedal. This tends to make the rpm drop slowly when shifting. This is suppose to help reduce emissions.
I have a performance tune on my 02 Ranger that changes the way it decelerates and takes advantage of engine braking. When I return the tune back to stock for emissions testing I get this slow drop in rpm between shift and it drives me crazy. I also don't like it when I let up on the accelerator pedal to slow down and it doesn't slow down very much forcing me to use the brakes more. I am very happy when I can get it back on the performance tune so it can have the good driving characteristics again.
2002 FX4 Bright Red Supercab 4.0 SOHC, manual 5-spd & Tcase, 33" BFG MTs, K&N air filter, Modified air box inlet, Gibson SS cat. back exhaust, Bama flash, Hidden Hitch round receiver, Rear helper air springs, Electric trailer brake controller, Line-X bed liner, WAAG bar with KC lights and Wildernest shell.