spark plug cap sends sparks to engine block ( GTX DI)

[alexandria]

finally, I got XPS oil and my GTX-DI is running normally for about 6 hours. Suddenly it became very rough then died. I replaced the spark plugs so it fired up again. I noticed that one of the spark plugs caps is very loose and sparks are going from the cap to the engine block ..... I wrapped the loose spark plug cap with electric tape with no luck. ski runs very rough with no power at all (mostly on one cylinder) ... the spark plug cap is not available for the DI model !!!.... need a quick fix to save the remaining few days of the summer season.
Can I cut the spark plug cap and insert a generic car spark plug cap?
can I put WD-40 inside the cap so that the coil is free and stick to the spark plug

any other ideas.... please help