So would that be a boring and piston issue or crank issue?

 

If you are asking me, it's a tuning issue. The reason you blew the cap off was because your bike didn't have the vent fix.

 

I’ve owned the bike for 3 years though and this is certainly not the first time or the hardest that I’ve beat
on it with no issues. Now after the cap blew off I’m experiencing blowby

 

Blowing the cap is a common issue without the vent update.. It don't happen all the time.
And you did a leakdown test to verify this? How long with the current top end? For sure the motor needs a tune.

 

current top end has maybe 3-4K on it

 

Well to reply and fill you guys in a bit, finally dropped the bike off at the builder this week and he called me to tell me that I broke the thermal jet off in the rear cylinder which is what caused the over-pressure and oil being pushed out of the breather. Cases will have to be split.

 

Not over pressure but over oiling / sumping. So who caused the oiler to break off? An easy way to do it is to rotate the motor with the cylinders off but the pistons on the rods and a rag stuffed under the piston to keep crap out.

 

I have replaced piston oilers without splitting the cases; very carefully of course to avoid dropping one into the sump. If the OP can retrieve the broken oiler pieces and repair any damage to the piston or cylinder the issue could be addressed without splitting the cases.

Having said that, the OP needs to know how the oiler was broken; seems to me that is pretty important to know.