I performed a compression test on my 165,000 mile Maxima this weekend in addition to installing the pipe. Here's the results:

1. 190
2. 175
3. 189
4. 185
5. 190
6. 187

I believe the factory service manual said 128 is the lowest limit and 175 was standard. Furthermore it said that the biggest difference between cylinders shouldn't be anymore than 14.

When I bought the car, it actually tested lower on the compression. I used a differenct guage though.