I just put a new downpipe on my 1993 240.

Mine is a Michigan car. No EGR

However, the spin-flange downpipe I ordered was for EGR. The only diiferencr is that it cam with a theadeed bold to plug the threaded hole in the side of the downpipe, where apparently some typt of EGR system tube/pipe attached if your car had EGR

Mine does not. So I plug the hole with the bolt and a copper washer.

The CAT was spin-flange also, with an approx. 2" diameter tapered steel ring to seal the 2 flanges on the downpipe and CAT.

My new CAT had the standard hole for the O2 sensor

I also used high temp silcone fireplace sealer (came in a cauling tube) to help seal the connection where the 2" dia steel ring was.

My CAT was a BOSAL? $150. i think. came with the steel ring and clamps

my downpiper was $108. from O'Riely's auto parts

Suggestion, when you bolt the two pipes together use stailess nuts, SS bolts and SS lock washers, with anti-sieze.

I also replaced the 3 exhauste manifold studs where the downpipe connect to with Stainless steel studs. I bought 50 mm long SS bolts at the hardware and made my own studs.

I also used SS nuts to attach the downpipe (w/ a new gasket) to these 3 SS studs. Also use anti-sieze here as well

You'll be back here in about 2-3 years