Over the last 3 days I have fit a "Welly" fmic,new silicon T I P ,done the SAI delete and fit an oil catch can piped to atmosphere. Fiited the 330 ohm resistors. Everything was fine this morning,running really well then later in the afternoon it started miss-firing. Plugged in reader no codes came up,so changed all the spark plugs,no change. My car is a 210 bhp apy year 2000. Could this be coil packs ?