Aintbroke dontfix

Had a couple of replies to this in general section but any more advise appriciated. This morning in the rain, approached a large roundabout over A11 in 3rd, travelled around it in third off boost, then booted it in 3rd to get past Cambridge dawdlers. Then stutter and bang pop, then carried along as normal.
The car was fully warm, & I have a pipercross with holes drilled into bonnet vent to let more air in. Could this be the problem with water getting through the air filter. I dont want to damage my baby.

Aintbroke dontfix

Yes I am a nork, 2 posts sorry.