Grinding 400x header help.

I have a 14 trx400x and is bone stock. I have a uni filter coming with a 40 pilot jet also. If I grind the header weld will a 1 step up pilot be sufficient and can I safely grind the weld to the tubing walls w/out it cracking in a puddle? Thank you very much for the help. Someone said they ground the weld and the quad ran bad, but I have no air box/exhaust yet.