You cannot simulate 6 pips slippage with a normal price curve. Even if you could, it would not make much sense. Better check what caused the extreme slippage. Maybe some sudden price jump at entering or exiting a trade. You should see that in the log.
Forex slippage is normally in the 0.1 pip area.
Thank you for your advice. I checked the log file, it is a very long list. But I can not find slippage inside. Is there a way to read/output slippage trade by trade?
