Still not bad. Who tuned the mustang on e85? Lund, vmp? Several good tuners out there. Fbo e85 mustang can easily make 450 whp. Yeah its heavier.. 3700ish. But even at 3050-3100lb a gti keeping up or even pulling a car on a mustang that could very well trap 120 + is very respectable.
I had a 14 GT with full cobra jet intake package with big Oval Tb. Did a ton of logs on 93 pump plus Octanium additive. Lund was dialing in 32 degrees timing with zero knock. Car ripped. Lund and AED are top shelf. Pulled half a car 2x on 15 m4 dsg with Dinan exhaust and piggy 50-125 mph. Ran as good as stock 15 c7 auto.
My 5.0 was on e85 with Lund flexfuel tune, they're a good platform to start with but insurance and the generalization of the group you're acquainted with drew me away. Living in a big city sucks for insurance with no accidents or claims. lol