When looking to redo my suspension, I was originally going to go with KYB AGX/Vogtland spring combo. But then $$ comes into play, so I had decided on GR-2 to save a few bucks with the vogtland springs..
But when doing my research I found that there are a few different part numbers floating around for the grand prix KYB struts.
Most places will sell you KYB GR2 #334227 for the front and GR2 #334228 for the rear. (both struts are silver in color) This is what ZZP and Wbody store will sell you.
Some places were showing KYB Excel-G #339015 for the front (black in color) but still GR2 #334227 for the rear (silver in color)
So I called and talked with a tech at KYB and told him what I was doing with the vogtland springs, and he recommended KYB Excel-G #339015 front and Excel-G #339148 rear (both black in Color)
ok, now I was confused.. but he explained..
The Excel-G struts (339015 and 339148) are newer recently added models that are correct application specific replacements for the Monte Carlo and Impala with the FE4 special handling package, which supposedly have a slight 10mm lower ride height and different rate springs. These struts were built to provide an aftermarket replacement that would retain the characteristics of the FE4 special handling package, as the currently available GR-2 struts would have been a downgrade in performance.
He said both of these would provide tighter handling over the GR-2 models, especially the rear, which was designed for the extra rear weight of the impala/monte carlo. Theoretically this could help tune out some of the understeer that is built into the w-body platform.
It was his opinion that since my goals were sportier handling to give these a try. He still recommended the GR-2's for original equipment replacement.
I have since ordered and received the KYB Excel-G 339015 and 339148. Just waiting for my vogtland springs to ship (backorder from AJUSA), and all new monroe strut mounts/plates. Cost is comparable to GR2 (maybe just a few bux more).
This will be going on my daily driver 2000 GTP along with a 19mm GMPP solid rear sway bar, and Dorman solid 34mm front bar with TPR bushing upgrade, and of course the Vogtland springs.
I'll report back once all is installed and road tested.
Jeramie