Bitter Bitter Bitter

I have brewed two pale ale kits. One was extract and the other all grain. Both have turned out okay but exceptionally bitter. The extract kit had steeping grains. I never exceeded 170 degrees with the water (no notes in front of me) but the gravities were on point both times (starting and final). They were left for two weeks in the primary and two additional weeks in the secondary. Bottled and conditioned for three to four weeks. They are good but.... WAY Bitter.
Brewers Best extract w/grains
Midwest Sierra Nevada Clone.

What else could be causing the off taste? Any ideas or suggestions would be helpful. I'm brewing the Midwest Simcoe IPA this weekend and would like to have a better result.
Thanks everybody!

Did you do full boils?
If you did, did you reduce the amount of bittering hops?

The extract was a partial boil (This was one of my first kits and I thought I was doing good by "sqeezing" the juices from the bag). The all grain was a full boil. Was I foolish to assume that an all grain kit with full boil water measurements would calculate the necessary hop additions/subtractions?

Do you know the Sulfate levels of the water you are using?

SO4 can accentuate bitterness if in high levels (400 ppm or greater, IIRC) I ask that becuase I used to have that problem specifically with Chinook (and I love that hop, only I realize that SNPA uses Cascade).

I haven't checked the water ph however (I know I'm a rookie) I used the BeerSmith water profiles for my area (DC suburbs). With that and the water filter from my fridge I figured I was alright but no I don't know the exact ph or sulfer levels of my water.