Forte treatments seem to have a good name, a bit pricey though. Although most engine treatments (Forte, Wynns, STP etc) are all essentially the same if you look at the ingredients on the labels.
Modifications: Blanked EGR Valve 265/75/16 Marix Lions Pro-Comp Steering Stabiliser Rough Country Shocks + 5" Suspension Lift UCA Ball Joint Spacers + Low Profile Bump Stops Stainless Extended Braided Brake Lines 1.5" Body Lift CB Lowered Front Diff Hangers Grooved and Dimpled Front Brake Discs Front and Rear Recovery Loops Petrol Cap on a String Secondary Air Injection System Removed Removed Front ARB
Soon to have 5.13:1 Diff's Got the Diff's just need to fit em
I prefer not to flush my engine as It can disturb deposits that actually help stop leaks. I think if you flush it should be done from when the engine was new.