IIRC the stock mech fan pulls almost 4000 cfm on its own. I think you short changed yourself. Does it overheat on the highway too? What about your radiator cap.
1987 XJ 4.0 I6, Peugeot tranny, NP231, AA SYE, 8.25" 29 spline, Dana 30 (HP), Rusty’s 4.5 inch coils, BDS 5500 4.5" shocks, 5" junkyard bastard pack, Rusty’s Adj LCAs, RC Quick Discos, JKS BPEs (front and rear), Aussie Lockers (front and rear), Durango steering box, and Removable Doors!