taison,
i would recommend changing to bilstein shocks. when i first installed the H&Rs, i kept the stock shock and it was ok. but after 2 months, i put on the bilsteins and it made a big difference. the stock shock with H&Rs at high speeds on the frwy was kind of tipsy/wavy (not confident) so i would definitely recommend doing the shocks at the same time, plus it'll save you on labor costs.

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1997 E420