I had the AHC removed by Slee when I bought my 2000 LX470. Lexus estimated $3600 just in parts to fix it. Good thing I had a $3000 repair credit from the dealer. I had Slee put in the OME 1.5" lift medium suspension with diff drop and SPC UCAs ate my $3000 credit but well worth it. The...
My LX470 gets about 15 mpg, highway, around town at 9000 ft or down where I live at 6000 ft elev, doesn't seem to matter. Not great but consistent. I would check your spark plug wires make sure (no kidding) it's firing on all 8 cylinders.
Do you have the stock shocks on, or did you replace them with OME? If you're using OME shocks they're the culprit. Switch to OEM, you'll lose nothing but the headache.
I had Slee replace mine with their 1.5" OME Medium lift kit with SPC UCAs and a diff drop. I would highly recommend that except would go with stock OEM Landcruiser (not LX470) shocks. It will be very capable off road and ride really nice around town.
I had the Slee Med 1.5" lift kit on my LX470 (AHC replaced because it was broken and way too much money to fix). I started out with the OME Nitro Sport shocks, they were really harsh, comparable to my 56 Dodge Power Wagon with 13 leafs on each corner. I went with OEM and they were great, but...