Swirl flap delete is cheap insurance. The flaps can break and cause catastrophic engine damage. Delete them preventively and never worry about it again.
On the M57 its absolutely necessary as a preventive measure. The swirl flap screws can come loose and get sucked into the engine, destroying pistons and valves. The repair cost is 5000+ EUR. Swirl flap delete blanks cost about 30 EUR and take an hour to install. Its the cheapest insurance you can buy for an M57. The only downside is slightly rougher idle when cold, but thats a small price to pay.
I deleted the swirl flaps on my 530d as soon as I bought it. The previous owner didnt and one flap was already loose. Got lucky it didnt drop into the engine. After deletion, the car runs fine - maybe 1-2% worse fuel economy at idle but who cares. Do it before its too late.
