I've had the Cobb TBE sitting in my basement for almost 2 months now and I got fooled into installing it yesterday since the weather was great at lunchtime. Then it started to pour and I got drenched. Lots of fun. Here's some notes about the install and performance. A lot of these things I've seen elsewhere one at a time, so I'm just consolidating everything I know.
1. Get a friend to help. It can be done by yourself, but double the install time. Took me about 4-5 hours mostly because of stuck bolts.
2. Use penetrating oil on all bolts and tap them to loosen them. You will still shear some bolts if your car has any significant miles on it. The good news is that I didn't have to re-use any of the holes where I sheared a bolt (4-5 of them).
3. Get new spring bolts for the midpipe because unless your car is pretty new, they will shear. (I forgot and had to fab up some replacements, but thankfully I have a sizeable shop and the tools and parts to do it).
4. Put together the midpipe and axleback of your new exhaust before you put them on the car. Much easier.
5. Get ramps or a high lift jack. I have a normal lift jack (15") and the car was barely high enough to work on once I put it on the jack stands. This really goes for working on cars in general. Invest in a high lift jack (20") and you'll be much happier.
6. Take the intercooler off. I've seen a lot of stuff saying that you don't need to do this, but it only took me 10 minutes to remove it, and another 10 to reinstall it. If your car is pretty new then you can probably get away with leaving it on, but I couldn't get leverage on one of the stock heat shield bolts with any tool I have (and I have a lot of tools) and had to take off the intercooler.
That's all I can think of for now but I'll edit the post if I think of more. I lost one of the DP bolts somewhere along the way, but for now 4 bolts is fine and I ordered another one from the dealer. I also found that my DCCD sensor was broken off at the rear diff. Still works, but I'll be replacing that too.
I've heard this before but words can't describe what a huge difference stage 2 makes. I'm still not sure whether stage 1 really made any difference. I know it did, but it was a small enough difference that I could convince myself my mind was playing tricks on me. I had my car at stage 1 for about 2 months and a few thousand miles.
Stage 2 is a huge difference over stage 1. HUGE. ENORMOUS. The car is a whole different animal. I got on an highway onramp today and a truck coming the other way didn't yield like he should have. In 2nd gear at 25 mph I floored it and the car went into a 4 wheel power slide instantly. Holy crap. My car at stage 2 is nothing like the stock car was. I got the exhaust used for $600 which is really good for a catted Cobb TBE. I got the AP v1 for $300 used which is also really good. Add in the gaskets and for a little under $1000 I got to stage 2 with premium components.
I started up the car when I was done with the install and as soon as I walked inside my wife said "Your car doesn't sound good. It's really loud." I would have to agree with her, the Cobb exhaust at idle is pretty loud compared to stock. At higher RPMs though, it's not that much louder than stock and it has a really nice exhaust note. It also exhibits absolutely zero resonance. If you know anything about aftermarket exhausts, you know this is really hard to achieve.
Five thumbs up to Stage 2!