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About a month ago I was on my way home and a Chevy Cruze tried to pass me, I put my foot to the floor and my car sort of choked, sputtered a little bit but it finally took off after a couple seconds. Wasn't sure what it was but I didn't notice anything after that in the power or any sputtering, etc.

Tuesday I was on my way into town to pick my niece up from work and when I was going up a hill (boost was right around 0) and it started sputtering again like it just didn't want to go uphill, the service engine soon light started blinking on & off - I let off the throttle a bit and it smoothed out about 30 seconds later. I checked the EGR the other night and from what I could tell it was fine, reinstalled it but left it unplugged and went for a test drive. I drove about 8 miles around 65 mph and the car didn't shift into overdrive till I was coasting down a hill almost back home. Ran the code and it was P0401..

I've wanted to do a tranny service to the car when I got it with 140k but just kept putting it off and it hasn't gotten done. I have no other car to drive so I've been driving it all week just to work and back with no problems as long as I don't pass anyone or go over half boost uphills. Normally it drives perfect so long as I keep my speed around 65-70 but if I drive slowly (50mph) for awhile and then hit 65mph it will take a minute or two to shift into overdrive. Checked all the fluids and they were all fine, and I plan to do the trans service this Wednesday when I get paid.

So long story short, it sputters and chugs a bit anytime I go over 0psi boost, but drives / shifts out perfectly if I stay around 65-70mph. When I downshift into 3rd and pass someone mid throttle it is fine but if I keep it in drive and actually make the pass, the service engine light will blink for 30-45 seconds till it smoothes back out. I'm at a loss here and my dad isn't familiar with the supercharged motors or anything newer.

Any help is much appreciated, as always guys! Thanks in advance for the advice!

That sputtering you are experiencing is a misfire. I would normally suggest you look at plugs and wires (to start) but that P0401 code indicates a problem with the EGR valve. The problem could be because the valve is not opening or closing, there is a blockage in the EGR tube, the EGR valve has failed, or the EGR tube is cracked. Remove the EGR valve and tube, inspect and clean them from any carbon build up. You also want to check for any vacuum leaks. If that doesn't clear things up you may have to replace the EGR valve.

If you have a scanner, keep checking to see if any other codes are popping up, like a P030X (X is 0 to 6). It is possible for the EGR valve to cause the misfire, but I would not want you to spend the big bucks to replace it, only to find out the misfire is caused by a bad spark plug wire.

How can you tell if the EGR has build up? I took it off & looked inside, looked normal to me, black but it was open but the valve isnt stuck, it almost seemed like it was too flimsy though because tilting it around I could hear a little ting inside the EGR but didn't really sound like anything was broken?

Put it back together and left it unplugged, doesn't change anything. Did a tranny service on the car today though & it's def running better but still not 100%

When I bought the car I had a misfire issue & this isn't it - no misfire codes at all either. I checked all around the tube as well, could not find any corrosion or cracks or splits?