Using indicator Slows Down speed of backtesting,Why?

Hello Guys, I have Create a simple indicator which shows a moving average on OsMa indicator

everything works fine, but when i want to use it from an EA The backtesting Speed's is too slow

I call it from EA like this

OSMAmain=iCustom(NULL,0,"OsMA_SIGNAL",FastEMA,SlowEMA,SignalSMA,MAPeriod,MAMethod,0,0);
OSMAsignal=iCustom(NULL,0,"OsMA_SIGNAL",FastEMA,SlowEMA,SignalSMA,MAPeriod,MAMethod,1,0);

Why Speed is too slow?

What do you think?

Thanks for Helping

The Code for indicator is below:

//+------------------------------------------------------------------+
//|                                          OsMA With MA Signal.mq4 |
//|                          Copyright © 2010, Farshad Saremifar     |
//|                                                                  |
//+------------------------------------------------------------------+
#property  copyright "Copyright © 2010, Farshad Saremifar"
#property  link      ""
//---- indicator settings
#property  indicator_separate_window
#property  indicator_buffers 2
#property  indicator_color1  Silver
#property  indicator_width1  2
//colour for signal line
#property  indicator_color2  Red
#property  indicator_width2  1
//---- indicator parameters
extern int FastEMA=50;
extern int SlowEMA=210;
extern int SignalSMA=80;
//external variable for the period of the signal line
extern string MA_MAMethod =  "-------(SMA=0,EMA=1,SMMA=2,LWMA=3)------";                           

extern int MAPeriod = 11;
extern int MAMethod = 0;
//---- indicator buffers
double     OsmaBuffer[];
//we need an additional buffer for the signal line
double     MASignalBuffer[];


//+------------------------------------------------------------------+
//| Custom indicator initialization function                         |
//+------------------------------------------------------------------+
int init()
  {
//---- 2 additional buffers are used for counting.
   IndicatorBuffers(2);
//---- drawing settings
   SetIndexStyle(0,DRAW_HISTOGRAM);
   SetIndexBuffer(0,OsmaBuffer);
   SetIndexDrawBegin(0,SignalSMA);
   SetIndexLabel(0,"Osma"); 
    SetIndexStyle(1,DRAW_LINE);
   
   SetIndexDrawBegin(1,MAPeriod);
   SetIndexBuffer(1,MASignalBuffer);
   SetIndexLabel(1,"MA Signal"); 


   
  
   return(0);
  }
//+------------------------------------------------------------------+
//| Moving Average of Oscillator                                     |
//+------------------------------------------------------------------+
int start()
  {
   int limit;
   int counted_bars=IndicatorCounted();
//---- last counted bar will be recounted
   if(counted_bars>0) counted_bars--;
   limit=Bars-counted_bars;
//---- osma counted in the 1-st additional buffer
   for(int i=0; i<limit; i++)
      OsmaBuffer[i]=iOsMA(NULL,0,FastEMA,SlowEMA,SignalSMA,PRICE_CLOSE,i);
//---- ma signal line counted in the 1-st additional buffer

 for( i=0; i<limit; i++)
     MASignalBuffer[i]=iMAOnArray(OsmaBuffer,Bars,MAPeriod,0,MAMethod,i);
   



     
   return(0);
  }
//+------------------------------------------------------------------+