Depends on where you go to test, early 49 state 124's did not have pre-cat's. Unless the tester know the Mercedes product line and fails the car for a visual the car will pass the dyno no problem. As with any smog test be sure the car is good and hot before testing. The pre-cat was installed for warm up conditions.

Regarding glass packs; I am not a fan of these, they are shrill and most are rather restrictive.

Steve