De-tuning a xud for economy?

[Andy annear]

Never cleaned the in tank strainer, checked it after first few tanks of veg but looked fine to me, im reluctant to put petrol in it, it may just be by chance but in both my 106 and this 306, shortly after putting petrol in with the veg my glow plugs shat themselves, no idea if petrol could cause that but didnt seem to help with much tbh with starting etc, but then again everyone cant be wrong!