Sorry I did not respond sooner.  I was out of the office. I tried your code and did not see the problem; I saw the correct output noise. The only difference is that in my "test2" module, I have


input in;
output out;
electrical in, out;

i.e. you may need to insert the "input..."  and "output..." lines. Also, the coefficients are the coefficients of z-1, so you had it right the first time.