Bilstein has been my 'go to' shock for many years for any vehicle that they make shocks for. The original Bilsteins on my 02 FX4 started to get soft around 100K miles. I replaced them with Bilsteins replacement for that application. They were a little firmer than the Ford OEM Bilstein shocks when new. I always thought the original shocks needed to be a little more firm. I guess Ford had them tuned primarily for street use and minimal off-road usage. I feel Bilstein got the tuning right for off-road usage.
I find it hard to believe your Bilstein shocks are causing your problem.
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.