There are different varieties of ST coilovers, the ones the site you linked to carries is a very basic progressive coilover and is totally non-adjustable. The ones listed above may or may not be those...I'd ask those questions first before dismissing his offer. If you don't know what I'm talking about, I'd highly suggest you do a bit of research before making a purchase.
Just read your thread...the coilovers you had on your last car were linear springs with helper springs...a hole different ball game. Also, on this car you already have sport suspension, unless you're strictly going for asthetics, I don't know that I'd change out stock for a lower end coilovers, especially a non-adjustable one.
Also, the HPFP isn't going to be your first limiting factor to running higher percentages of E85...the LPFP is and there are already fixes out there for that.
2008 E88--2 years on 100% E85. Too much to list..
2008 E60--JB4/MHD--FBO and under development
2011 E90--Fuel-It! Stage 2 LPFP + TBI--Pure Stage 2 Turbo--JB4/Flash--VRSF 7" FMIC--DP 538/581
2013 Mini JCW--Tune--DP--FMIC--a couple Fuel-It! goodies