Rate my fibonacci program

(define (fib n)
  (((lambda (x) (x x))
    (lambda (fhelp)
      (lambda (remaining cpair)
        (if (zero? remaining)
          (cdr cpair)
          ((fhelp fhelp) (sub1 remaining) (cons (cdr cpair) (+ (car cpair) (cdr cpair))))))))
      n (cons 0 1)))

>>4
There a problem with the given level of nesting? It's using the Y-Combinator to achieve anonymous recursion. I don't think I could use any less nesting here without abandoning that.