What was limiting your speed to 135ipm with the old PC?
Generally, the only reason your PC will limit your speed is if it can't run at a high enough kernel speed. So if you were''t running at the maximum velocity for whatever kernel speed you were using, a new PC won't go any faster.
Say you were running as fast as you could at 25Khz kernel speed, but the PC wasn't capable of running at 35Khz kernel speed. IN that case, if the new PC could run at 35Khz kernel, then it might be able to go faster.
Generally, it's the motors torque that limits your speed. Not usually the PC.