Brian,

Typically a set of equal length header primaries into a collector bring little advantage if dumped into a street exhaust system.

Also typically the Benz factory cast iron manifolds are very efficient as cast iron manifolds go. The advantage of cast iron is better silencing and less heat dissipated under the hood.

I was glad to see you got the maiden oil change knocked out and that you drained it from the bottom.

Have a great day,