To factorize the expression (3a-1) -6 +2, we can first combine like terms.

The expression can be rewritten as 3a - 7.

Now, we can factor out the common factor of 1 from both terms:

1(3a - 7)

Therefore, the factorization of the expression (3a-1) -6 +2 is 1(3a - 7).