I don't have a IX but my VIII broke up bad at WOT and it turned out to be an exhaust leak....just something else to consider.

 

Where was the exhaust leak? If it was before the first 02 then I could see it acting up but downstream not so much... I have never heard of an exhaust leak causing a car to break up before but I am pretty new to this game.

 

I had two big leaks...donut gasket at the downpipe and the other at my high flow cat on both sides....replaced the donut and two 3" gaskets (both sides of the cat) and the problem went away.

I have the 3" Vishnu Standard exhaust with high flow cat....

 

Quick update bought plugs "ILFR7H" ... but when pulled old Plugs... they were IKH24 witch i know are a step colder than stock ... Sooo going to buy IKH24. Previous owner must have put them in they were also tuned with them in so might as well put those back in... and as for the Price of ILFR7H we have a local Part store that sells them for 9$ a plug called bennett auto supply I know they are in central and south FL so... worth a tip if anyone is also needing plugs in stock heat range around here