Acceleration Issue with my 2002 VW Golf (83k miles)

I let the car sit in the cold for a week outside. I am from the Chicago area, so it can get pretty cold. When I came back, the car started fine, but when I tried putting it into reverse or drive, it was quite a bit shaky. I couldn't accelerate very easily. I let it warm up a bit, then tried driving it around the parking lot. The engine was riding very rough and the check engine light started flashing. After letting it sit while running for a little bit, the light stopped flashing but stayed on. I drove it around a little and the acceleration got a little bit better and the roughness pretty much stopped.

I drove about an hour and a half with the car and it seemed okay, until I would need to accelerate quickly. If I press the petal too much when it is in 2nd or 3rd gear it wont accelerate but only slightly. Sometimes if I press the gas too much it will shake a lot. On the highway it would not accelerate over 70 mph and it stays a little over 3000 rpm.

I ran the codes and it gave me a P0301 and a P0342.

What do you suggest I do? Do you have any thoughts on what it could be? I have done a little work before on my old car, but I don't know a whole lot. My mechanic is busy until after the holidays.