Is It Tough To Install Catback Yourself?

Well the deed is done folks! It was fairly easy until i ran into a problem that was a PITA. I got the drivers side done easily but when i started on the passengers side thats when the fun started. They welded the hanger on the muffler too low. It wouldn't fit in the supplied bracket. It was about 2 inches too low from where it needed to be. When i raised it up the muffler was riding on the drive shaft. I had to fab up a new hanger to fit between the rubber grommet on the bracket to the hanger on the muffler. It took about 4 hours in total. oh well, it was worth it. IT SOUNDS AWESOME!!!! I can barely hear my stereo when I get into WOT. I did notice a power gain as well, I'm not talking huge numbers here but i could definitely feel the difference. There seems to be better throttle response and smoother acceleration. Thanks for the advise guys. A lot of it came in handy. I have to go to work at 5:30AM tommorow so we'll see how the neighbours like me now. :D Anybody know how much horse i should have gained by adding this beast?