Stock springs have 78-82lbs of pressure seat pressure on average at 1.380". If you are over 35psi(boost or drive presure) and 3,800 rpm, stock springs do not fully control the valvetrain. This allows a few negative things to happen. First, valve float, which can cause serious damage to the valvetrain. Second, intake and exhaust valves can be blown open by boost and exhaust drive pressure which allows reversion. Reversion can hurt your power potential by allowing exhaust gasses to enter the cylinder on the intake stroke. Inert gasses in the exhaust, when re-introduced into the cylinder shield the fuel particles from oxygen in the cylinder. This does a few things that negatively affect power. It increases the time delay from start of injection to start of combustion, it decreases the maximum pressure and maximum temperature reached in the cylinder and it increases the total time needed to completely burn the available fuel. Correct valve spring pressure is a very important piece of power production.
We recently slightly lowered the pressure on our springs from 110# to 103#. Nose pressure has been lowered from 220# to 180#. Watch out for other companies that have nose pressures over 250#. Your cam will have a shorter life with 250#x2 (500#) versus 180#x2 (360#)over the nose of the cam. Don't just ask what seat pressure is when you are shopping for springs, ask what the pressure is on the nose(1.031" with OEM cams or .958" with the 188-220)
If you are running over 4,500 rpm with a large cam, we suggest going with our 103# springs with dufferent heat treat and shot peen, for better longevity in extreme applications, as well as our light-weight 4130 or titanium retainers.