if you melted a spark plug end i would be checking the air fuel mix this tends to be a severe warning that you are running too lean,the next sign would be cooked rings resulting less compression and or a hole melted into the top of the piston,i have seen this happen before and it's easy to avoid.Check the fuel pump and pressure reg are still working correctly,if so ask tuner to recheck air fuel ratio are correct.Good luck and i hope this helps.