the 89 3.0's have EGR. 90 and 91 do not.

The EGR was eliminated when they switched the distributor setup and the ECU for sequential fuel injection.

If you failed for NOX, I would make sure you have a fesh tune up, fresh oil change.

Doing the Seafoam treatment first might help since carbon buildup in the combustion chambers can cause high temps in the CC's which can cause high NOX. HTH. If it fails after that, try a new cat.

99 Gen 2.5, fixing blown head gasket
89 SWB- 33's, ARB Front locker, SR rear locker/axle, SR F brakes, winch, WST Offroad Armor all Around, 2.85 Aussie T-case Gears (SOLD)
Sold: (2) 95 SR's, 86 SWB, 90LWB, 91 LWB
-Can Change a timing belt in my sleep..