A lot of people on the Stratus forums lower their cars, because performance mods are expensive. Many recommend not getting the AGX because the GR2s work fine and provide a firmer ride than stock anyway. There is also a problem with the AGX adjusters breaking anyway.
Like I said, if he's like most people, he won't be using the adjustments anyway, he'll just set it and leave it. So, it offers very little for the additional $250, which is more than enough to buy the GMPP kit itself. Just something he'll have to decide for himself.
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'13 Mustang 3.7V6 - MT82
'00 GP SE (L67 Swap, XP, Headers, 3.25")
'98 GTP, '01 Bonne