I was at a local workshop,and noticed a bare RB26DETT head. The exhaust ports each had a "bulge" that seemed to be factory cast( I haven't seen many heads actually bare and off an engine to notice this cating thing...). The extend a reasonable way back into the head,and I'd offer an opinion that they'd take up a reasonable bit of real estate in the port,flow wise. The front three cylinders' bulge was facing,I think, rear + lower in the port,with the rear three cylinders facing forward + lower. I've heard a theory that they protect a waterjacket,but I've also heard that workshops grind them down to improve exhaust gas flow...so,no waterjacket. Are they fine on a standard engine,but removed on bigger power-up jobs? Nissan wouldn't have put these bulges there because they were bored. So;what gives?