Just taken my s type r for its m.o.t. which it failed on the emissions 1 bank high and 1 bank low i did have a p1646 engine code so replaced the lamda sensor the code indicated to find no change then decided to put 2 lamda foolers on and this didnt work either so a little confused on wot to do next. do i replace all 4 lamda sensors. or could it be related to the fact its a( green racing version) with 460 bhp and maybe needs remapping ?

 

I think you've spotted the problem. Find out what modifications were made and undo them.

 

Mine failed emissions test due to faulty coil causing misfires with no codes

 

foolers? Can't possibly get sane emissions if the PCM doesn't know what's actually happening!

Leave the tune in and use proper sensors.

You could help yourself by getting an OBD tool with live data and watching LTFT per bank, at idle. If not near zero, it's unhappy. Elm327 is about a tenner.