S4TNT

For a reasonably mechanically adept person, (remember, I am talking ONE person) how hard is a cat back exhaust install with 1 being a piece of cake and 10 being near impossible to get it right. Asking with regard to a Milltek system.

Milpitas2.7T

3, with proper jack stands/jack easier with air tools

Ferris TMK

Don't use air tools you're only looking at 20-30lbs max torque..

UberVier

It took me 1.5 hours to get my VM1 done by myself. Biggest PITA was having to hold up the whole thing by yourself. This was even more of a PITA seeing as how the stock system weighs about 6 tons. Seriously.
Only tools I needed were 13mm socket for the sleeve clamps, wd-40 to help get the rubber hangers loose, and a BFRM (big f'n rubber mallett) to knock the new pipes into place (ie flush onto the cat outlets, but this may be diff w/ Milltek).
It was not that bad, I would say 6-7 due to the fatiguing weight of doing it yourself and having to be in awkward positions under the car. And this was just with the car on ramps, a lift would make it a 4 on the scale.
It's doable, and you'll appreciate it more if you DIY.

N10S

I recently installed a Forge Milltek exhaust and can give you the highlights from my perspective. Note: This install was done on a hydraulic lift which gave easy access to everything. I paid to have the job done, but assisted (later more than I had anticipated)with the project.

1) Removal of the stock exhaust was extremely easy. After unbolting the hangers and loosening the front exhaust pipe clamp connections the stock exhaust just about fell off. I expected some kind of a fight, but this part was easy.
Rating = 2

2)Re-installation of rubber hangers is not to tough although it is harder when removing from the factory exhaust than when re-installing on the Milltek. A nice bolt-on hanger retainer makes this a pretty easy job.
Rating = 3 to remove, 1 to reinstall
Average rating = 2

3)Re-installing the exhaust is a little tricky because you are trying to get all of the pieces to match the correct locations in the driveline tunnel, while maintaining level tips in the back. This seemed real easy at first but the initial install had clearance issues when hot, and I had to take the car back for exhaust re-alignment. It was good that I did because one of the nice saddle clamps up front did not get centered properly and was not clamping evenly allowing an exhaust leak. The clamps included are the best I have ever seen, but do be aware that if you let the sliding saddle move from center it will cause clamping interference. After re-alignment I drove home only to find that the exhaust hit worse than ever (bummer).

This prompted me to take the install into my own hands using ramps and chocks at home. This really wasn't to bad and I was able to better assess the situation. My first observations were that this is one big-*** exhaust, and at 3" diameter there really isn't a lot of room for it to fit. The other thing I noted was that the small casting tit that hangs down in the rear crossmember that the exhaust passes through before hitting the front muffler had been hitting. Before realigning I shifted the exhaust to one side and used a dremel to grind part of this square-edged aluminum tit off. This is really a bitch and I wished this had been removed when I had the car up on the rack.
After finishing my grinding job and re-aligning once more, my issues seem to have pretty much been resolved. Abrupt hits, drops etc... have still caused some very minimal problems and although it is a rare occurence that this happens I am certain that because I am a perfectionist, I will be grinding the rest of that stupid casting tit off before its all over. Perhaps you will not run into this issue but if you do make sure to wear safety goggles and a paper breathing filter to avoid breathing in metal dust!

Rating: Should be a 3 or 4 but because of the repeat work and close fit tolerances, not to mention frustration, I give this one a rating of 7.

Average for all facets of de-install/install
Rating = 5 based on my alignment and fit experiences and probably a 3 if you are lucky and hit the sweet spot for alignment the first time.

Hope this info helps!

By the way the exhaust looks and performs beautifully!! I am looking at adding the new Milltek downpipes and cats next (claimed to add 25-30 hp/25 ftlbs torque) and have heard that Milltek will also be making exhaust manifold/headers in the future.