Rough Idle and stalling

[JesseSVX]

A friend came by with his 92 and he's having issues with rough idle and it stalls when slowing down. His CEL comes on with and i checked the codes for him and it popped up 34( EGR solenoid valve inoperative) and 37 (O2 sensor 2 LH side)

My question is, is that is the O2 sensor the left side facing into the engine bay or sitting in the car?

And if it is the left side O2 sensor does this have any relation to why the EGR is faulty. I'm also suspicious that it could be that the pre-cat is clogged and is getting excessive back pressure and hence the reason for the bad idle and does fine when accelerating.

And how do i go about fixing the problem?, replace the O2 sensor and check the codes and if the code still pops up, should i assume the cat is clogged and replace that?