[Shotimes] Need Help With Codes

[Urbain, Michael H.]

Need some help please.  Here's the deal:

I have a 92 that has been running great.  I recently installed a SHOSHOP
Y-Pipe to my Dynomax catback (no other engine mods except K&N and removed
cone) and my "check engine" light is now on.  I suspect the 02 sensors but I
wanted to double check anyway, so I ran some codes.  This is the first time
I've done this and I came up with a couple of wacky ones so I might have to
run them again, but here goes:

KOEO - 172, 176, and 542 - According to the list this indicates that my
system is running lean and a fuel pump secondary circuit failure.  What
would cause this and what needs to be replaced/repaired?

KOER - 361 and 721 - these are the wacky ones.  Anybody ever seen these?

Now I can tell you that there is a strong gas smell so I suspected that I
was running rich, but maybe it's lean.  Would the 02 sensors cause this?
Also, my gas mileage may have dropped slightly which is also an 02 sensor
failure indicator.

I'm looking forward to hearing back from you experts!!

TIA

Michael Urbain
'92 Black