Is the compression ratio on the 2000-2001 sentra SE 9.5 to 1? Is the primera sr20 10 to 1 or 10.5 to 1? Also, if the CR is higher in the primera, are the pistons interchangeable for the 2K+ SE so that a higher CR can be acheived? If the pistons are swapped, how would this effect the stock ECU mappings? Thanks... Lee