i have 99 cobra 51000 miles installed mac l/t/headers car smokes now using lots of oil 4qts. in 1500mi. or less. compreesion is good 175/170 on all cylinders only smokes when i run it farly hard . i heard things about these headers .plugs have no signs of oil .i change to sync.oil at the same time could it be the oil. what have you heard about these headers. should i change back to reg. oil ,,any help plese?