I assume your using all the same type and heat range of plugs <img src="/forums/images/graemlins/smile.gif" alt="" /> Anyways just change them out with some factory plugs NKG's and see what happens. Don't waste your $$$ on any of those fancy aftermarket ones.

The two inside plugs burn different than the outside due to the design of the intake manifold. How many miles on these plugs?

98 Montero with cold weather package
96 Toyota Land Cruiser, fully locked Mall Machine :-)