CEL help please

After some hard accelerations on the belt route the CEL came on. I pulled the numbers:

Current fault P2187: system too lean at idle bank 1

Pending fault P0441: Powertrain evaporative emission control system incorrect purge flow

Cars running great but I do notice that RPM's at idle go up and down about +/- 100 RPM's then the CEL comes on again.

recent history; 2 weeks ago I had a CTS Turbo catback installed to my APR downpipe (we had to cut and weld it to the down pipe. I love the sound of it). Since the new catback I have filled my tank twice with the usual 91 (Utah) octane. Toped up my oil with about 500 ml (it always seams to be down a bit at around 2000 ml after last change)

Ideas: A quick search of this forum came up with maybe an exhaust leak has slowly formed with the new catback. Bad gas. Over filled the tank (I'm very carful not to though). Can over filling the oil cause these codes?

I did over fill the gas tank once and this code came up but replacing the gas cap seamed to fix that. That all happened a year ago.

Well, you can see the mods I've made in my signature. Please help if you have had experience with this. What do you guys think?

Sounds like an exhaust leak. Check the welds and check the bolts on the turbo to make sure they are tight. Did you replace the exhaust gasket on the turbo when you did the downpipe? Maybe the Gasket failed. Ive over filled my gas tank many times to the point where its overflowing onto the paint and never got a cel from that.

I'll check it. Thank you for your reply. It was only the catback I had installed. I've had my downpipe in for 2 years now. The downpipe had to be cut shorter to fit the catback in. Then I had the catback welded directly on to the APR downpipe so it could be 3" all the way.

I went to the dealer today regarding this code issue and they replaced the "Purge Solenoid" due to code P0441 and the "PCV valve" due to code P2187. All done under warranty.

Did these things just go bad because they are a weak links or did I cause this to happen some how? Any input in this area? I suppose I should start with understanding what these parts do.