I have an '01 4.4 w/ sls. Both the rear bags were porous and needed to be replaced at a cost of $722 last month from indy shop. When the bags failed, the car was bouncing so much on the way home from work I thought I was going to puke! Imagine my horror when last week the car was sunk down in the back in the morning. The shop found no leaks, but determined that one of the check valves or control valves in the pump must be leaking by. I was told that the valve is part of the pump so entire pump needs replaced at $822 for part alone. The car is constantly in need of costly repairs ($9000 in past 2-1/2 years). I might pinch off the line that leaks by and do without the sls. With the new bags, once it is pumped up, it seems to ride level and handle well. I'd appreciate any advice, as I'm sick of pouring good money after bad into this car. Thanks.