Need to speed up my code.

[blackknite]

I have to return a simple sum of the most present values in the array, ie [3,5,2,1,2,3,2,2] - > should return 4, because (2,2,2,2).
The array sometimes is crazy focking big, and I cannot pass the execution time limit on the website that im practicing.

My code now is like that:

def birthdayCakeCandles(ar):
    def count_em(x):
        fin = ar.count(x)
        ar.remove(x)
        return fin

    return max(map(count_em,ar))

ar.remove is to not repeat the iteration for every occurrence of a same value, but it doesnt even feel like a speed up, is it even cached in cpu this way?