Hi Funyoo, the basic sar system you created is a promising EA.
Parabolic SAR EA
If you are able to make it MTF(multitimeframe) and trade Only in the direction of bollinger bands channel between the default 2std and additonal 1standarddeviation bands, it would be better.
i.e. We trade only when candle/bars is between bbands default 2std and extra 1std channel because that's the 'smoother' part of the trend and we avoid being stopped out by the choppy/noisy portion of the whole trend...
For e.g, Determine buy or sell in the direction of 4hrs/daily(user input) bband 2std-1std channel.
Enter on 5 mins(user input) sar reversal when in line with 15mins/1hr(user input)sar direction.
Exit on 5mins(user input)sar reversal.