Sadly mate,if you manage to map it. i think it'll be dead by the time you do pod

i'd suspect the Crank clearances TBH... mates williams clio had exactly the same
as you are describing, and when he started it up you could hear a funny slight
knock... it was the big ends got him to turn that off pretty sharpish.. and the 'Tuner' had mapped it on a RR like it