Core i7 is currently 4 core, with 8 threads. It would probably be best to try tweaks for BOTH eight cores, AND four cores, to see which works better for you. The tweak for quad cores is Affinitymask=15, not 1111. In service pack 2 this is AUTOMATIC, but you could still add it anway and try between 4 and 8 threads just to see if either works better.

[JOBSCHEDULER]
AffinityMask=n
where
n                        num of cores scheduled
1  =                         1 core           0001
3  =                         2 cores         0011
7  =                         3 cores         0111
15 =                        4 cores         1111
31 =                        5 cores         11111
63 =                        6 cores       111111
127 =                      7cores      1111111
255 =                      8 cores      11111111
511 =                      9 cores   111111111
1023 =                    10 cores 1111111111
2047 =                    11 cores 11111111111
4095 =                    12 cores 111111111111
8191 =                    13 cores
16383 =                  14 cores
32767 =                  15 cores
65535 =                  16 cores
131071 =                17 cores
262143 =                18 cores
524287 =                19 cores
1048575 =              20 cores
2097151 =              21 cores
4194303 =              22 cores
8388607 =              23 cores
16777215 =            24 cores


Code:

1 2 4 8 16 32 64 128 256 512
1 1 1 1  1  1   1  1

1+2+4+8+16+32+64+128

= 255. 

http://blogs.msdn.com/ptaylor/archive/2007/05/15/new-tweaks-in-sp1.aspx