Depends what tax bracket you are in. If you are in the 25% bracket you will save 25% off your tax by reducing your income by Itemized Deductions or pretax contributions.
So for a 4,000 Contribution you will save 25% or 1,000.
if you increase it to 2,000 you save $500 of Tax.
To save 2,700 you would need to increase your 401K contribution by 10,800 (10,800 x 25% = 2,700) if you are in the 25% bracket. Your tax bracket might be different.
