First time post but have used you guys a lot past three years! (I apologize for the long post).

So here is my latest in a string of problems....

I have an '01 A4 1.8T automatic. About a month ago I began having problems with cold starts. When first starting car after it had been sitting for more than 5 hours, my RPMs would rev and the car would idle rough for about 30 seconds before everything settled. Subsequent driving would be fine.

I thought it could be the coil packs so I had all 4 changed under the Audi recall. Unfortunately the problem still existed. About a week ago I had my turbo blow while driving on the interstate. I just had it replaced with a new one yesterday.

The mechanic who replaced my turbo drove my car around for a few days to burn off the excessive oil from the blown turbo and said he experienced the same problem with the cold start. In addition, he said that the car had a hard time accelerating at times (especially up hills) but thought that was either due to 1) the excessive amount of oil covering different parts under the hood and exhaust, and that it would eventually burn off; and/or 2) the front o2 sensor needed to be replaced because there was not a sufficient fuel/air ratio (which he though caused the bad cold starts and sluggish acceleration).

When I began driving the car yesterday I noticed the usual cold start problem again and the acceleration problem. When driving up hills (especially from a stand still position), I had to push down the gas pedal further than normal just to get it going past 25 mph and the RPMs would be between 3.5k and 4.5k (normally it switches gears no higher than 2.5k. It probably was going 0-60 in over 20 seconds up hill. Once it got over 50 mph it leveled out but was still sluggish. Downhill or on level planes the acceleration problem was minimal.

This morning when I drove on the interstate it took the usual lag to get it going (on-ramp was uphill) but this time it misfired for a few seconds (CEL blinked twice like when coil packs went out but then CEL just stayed on and didn't continue flashing). The interstate ride for a few miles was sluggish at first but eventually leveled out. CEL light hasn't blinked again except for those two seconds.

After work I didn't take the interstate and drove back roads. Didn't have acceleration problems as much except for one big hill when car backfired once and struggled to gain speed up the hill. I drove over to Autozone and had them run codes. The following came up:

P0172 System too Rich (Bank 1)
P0300 Random, Multiple Cylinder Misfire Detected
P0301 Misfire Detected in #1 Cylinder
P0302 Misfire Detected in #2 Cylinder
P0304 Misfire Detected in #4 Cylinder

The CEL light was not on until it blinked twice. I assume the latter 4 codes were from when the CEL blinked twice (similar codes when coil packs went out). The first code is what I am asking about.

While my mechanic said I need to replace the o2 sensor and it would fix the problems, I've heard that the o2 sensor wouldn't affect my cold start problem as it doesn't even trigger until it reaches a certain degree. And the acceleration problem didn't occur until AFTER my turbo blew.

I guess my main question is could this two simultaneous problems be caused just by the o2 sensor? I am aware it could be MAF and am going to clean tomorrow so I know that could be it. I am also aware these problems could be caused by VAC leaks. I had all my hoses replaced a year ago so wasn't really sure if they would already be faulty. Oh and had spark plugs changed with coil packs last month. Any other ideas on what it could be?

Thanks for your help guys. I apologize if I don't sound real technical like the rest of you. I am by now means real knowledgeable about auto mechanics but I love to learn and work alongside my friends who are mechanics.