New to the site. Looking for some input.
02 is300 186k mi
engine mods only are headers, full catless exhaust, kn intake,
ok here's the issue
Before this happened the only problem i was having was the MAF was starting to go bad. The problems I'm having are new before replacing the MAF.

Ok when i cold start my is300, it has a horrible misfire, sounds like a boxer engine, you can smell excess fuel as well out the exhaust.
When semi warmed up but not misfiring at idle, when the throttle is applied and the engine is under load it begins to misfire to the point of dropping cylinder fire and running at half performance.
When the car has been 100% warmed up and driven it drives without misfire but if i down shift and get into high gear it dumps an excessive amount of fuel to point where you can smell fresh unburnt gasoline.
Prior to these occurrences by several months, I've replaced my plugs, wires, packs, cleaned TB,cleaned intake manifold, air filter recharged, valve gaskets replaced and replaced pcv. Since the problem i have replaced my MAF which has helped with the power problems i was having prior to this issue but the issue still remains. Only codes (outside of using Lexus software on Max me tool) are 3 O2 sensor heater circuit DTCs. P0135 P0141 P0155

Any help would be appreciated.
Thank you