With standard injectors and exhaust you'll see around 260 I guess, but I doubt BlackMac will take it to that as the injectors will be running at 100% cycle duty. Keep in mind Simon has tuned many, many more F6's than Black Mac.
Safe tune at 230rwkw? They could pour in a bottle of octane booster to get that extra 10rwkw from an F6. It's all well and good saying they will support a customer that has engine problems... but until an engine blows as a result of their tuning we have no idea what their support will be like. I could hazzard a guess but. I've dealt with them in the past, and the experience has left me with nausea when I drive anywhere near Morley.