02 Sierra idle problem

I got a 2002 sierra 1500 with a 5.3l. I just replaced both catalytic converters and y pipe. After I did this, I am having a few problems. First, when slow down to park or at a stop sign the idle drops way down and it dies. I cleabed the throttle body, maf sensor, and ran a can of seafoam and a can of b12 chemtool through it. It did this for a couple of days and now when the idle slows down the "check oil pressure" light comes on before it dies. Then yesterday the "check oil level" light started coming on. Is this all related, would the low idle cause low oil pressure, any ideas where to start?

Some fuel pumps are designed to shut off if the oil pressure drops too low (not sure about this year and model though). I would start with an oil pressure test at cold idle and then when truck warms up