I think ass sag is just a GP thing.

How many miles are on the current ones and do you have anything in the trunk/backseats?

New ones should raise any sag the old ones had. Just remember you are going to need an an alignment afterwards. You also could opt for intrigue springs which are stiffer (if i remember right) which would help if you had stereo crap or whatever in the trunk too. Not sure if they would help overtime to reduce sag tho.

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