1. The oil pressre gauge on my 78 300D (123), 171k miles, "pegs" the needle @ 45 lbs. Is this normal?

2. The exhaust system needs to be replaced. It would be nice if the car had a little more low-end "get up and go". Should I replace with original or something more free flowing?

The car runs good; no other serious issues...

I am new to MB and diesels. Any help/hints/suggestions greatly appreciated.

My other sleds are a restored 64 1/2 Mustang convertible and a 93 525i.