Today during break in off a new GRP engine i had some troubles keeping it running under rich conditions with de GRP #5 plug. The outside tempature was high enough so that couldnt be it. I changed to a OS. P3 plug and i finished the break in with no problems at all.

Question is: Is it possible to go back 2 the GRP plugs or wont it seal proper now? (dont ask why i want to change back )