Must be something with the tune then. How long have you used this tune and how long before this condition developed or was encountered/noticed? Is there an option for 'engine brake' in the tuning? With some performance vehicles, even when completely off the throttle there may still be some combustion occurring as a form of reducing the amount of engine brake.
Side note, to my surprise, it's possible to have a lean condition turn plugs dark and even foul them. Happened with a prior motorcycle. Based on every chart I thought the plugs read rich but my Brother took one look at the plugs and immediately identified lean. I enriched a little and all issues (not the issues we're discussing) were instantly diminished. I'm not saying it's lean. Just something to be aware of.
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Thanks again
The tunes been run for about 2 years and it was fine until a few months back then started doing this
Monitoring this last night you may be onto something
When viewing my afr.. when using the throttle and letting off it reads 15.5 max generally
When the bucking happens it jumps upto 18 or even 19
Thats the main thing so may be the lean part
There is no engine braking part of the tune however
My rmm was over torqued by some idiot at the garage around the time it started happening
It was at least 100 ft lbs
Didnt think that was relevant though