Noise could be a piston skirt collapse unlikely on a built Mountune engine using Mahle forged piston and a M400X or R map. Or more likely bearings.
Just get your existing block linear bored (if it’s a bearing) as in the future a matching numbers car is worth more, than a car with Mia-matched numbers and then a new Callies light weight crank, job done.
Lastly get the rods checked for still being true and straight. Mountune rods only come in a set of 4 and are mucho £££££’s
Tri-metal bearings are a good shout as an upgrade bearing, those are what Mountune use and sell
Good engine builds if you don’t want to do the above on your OEM engine
Devil Developments
Pumabuild
Matt Lewis
MSD
Their are lots and lots of good engine builders out their each with multiple options on rods pistons bearings cranks etc etc
RS Edition.
FPM375 Rocks
The rest of the “M” maps suck
