The slugs could be any number of aftermarket pieces, so “identification” by noise isn’t quite that easy 
CP/Pankle, Wiseco, Ross, CW, etc all make pistons for that motor. However just because their noisy doesn’t necessitate that it’s a built block. OEM’s can be noisy as all hell too after a beating. Easiest way to tell is with a bore scope down one of the spark plug holes where you can inspect the dome of the piston. If you don’t have one of those, and are doing the timing belt, you can easily see by pulling one of the pin access plugs on the front of the cases and rotating the engine until you can see the slug at the pin boss. The OEM vs forged pieces have drastically different pin bosses that you can see though those holes. Or if you pull the motor and oil pan, dead giveaway by looking at the piston pocket at BDC.
Early CP’s PWC was .004, it’s now down to .003 with their new alloy composition, however I typically setup in .0033-35 range for forced inducted engines that are “going to be abused”. NA get’s .003 regardless. Suby’s have a tendency to be noisy due to their short skirt design anyway and the increased PWC of a forged 2618 alloy slug just amplifies that. Just a by-product of the case design really.