$400 for a timing belt change is not so mentle priced. The cheapest place for labor I could find is $250 for just the labor, its pretty labor intensive as well but I can do it in 4 hours. I bought a new belt+tensioner and belt for $100 new, I also got cam seals and a new cam cap and front crank seal while I was there.

Sounds like the sjop that did it set the timing off because if its not pretty close then you will have like you said less power. Make sure the mark on the lower crank gear is pointed to the mark on the block and the cam gears are in the UP position. That sets TDC and route the belt on and loosen the tensioner bolt, turn the motor over 2 or 3 times and then tighten down the tensioner belt. Thats it, c-speedracing.com has an awsome write up on it with color pics.