Gen I or Gen II GTX2860r? I haven't seen any dynos comparing the two, but I would imagine it's better being Gen II lol.Go look at stratifieds dyno results as well as others on the forum for the GTX with stock fuel system and no additional WMI as OP said. You cannot run full e85 on stock fuel system, OP doesn't want to upgrade the fuel system. You cannot run 25psi to redline on 2860 without so much heat you need to boost octane rediculously, I have been in one on 93 in a 2860 focus st and you can feel it drop power after 6k rpm. And then for the gtx2867r well I have one in my car so rather than reading reviews and opinions I have actual experience driving both types. I have also driven a 2971r and I couldn't really notice the lag, I think it was maybe 200rpm more and it did have more top end.
If you read what OP wanted he wants something that will pull all the way to redline, not max out a 2860 and upgrade intercooler from the heat and WMI or vast amounts of ethanol.
Yes the 2867r can max out the stock fuel system, but only if ethanol is added. The fact still remains:
1. the 2867r will pull harder to redline than the 2860 and for regular 93 octane and up to e20 (on stock fuel) the 2867r will give OP more power at redline.
2. The 2860 will have slightly less lag 200-300rpm but will fall off up top due to smaller compressor wheel (see countless dyno graphs where people aren't running WMI or high ethanol content to counter the 60's inefficient compressor wheel for higher powers)
3. The stock fuel system will not do much over E20 for these bigger turbos which will see a result of around 370ish whp for the 2867r and 355ish for the 2860. I would suggest you drive the two in like for like circumstances before you quote other peoples opinions and experiences. By like for like I mean on similar setups and fuel like I did (93 for both). Just like you can run WMI for the 2860 you can also do the same for the 2867r and achieve higher numbers up high.
Note that the 2860 is a great turbo for low down response but it does fall off in power up top unless you are compensating with octane. The guy with the GTX2860 who I drove's car feels slightly more responsive than mine but again I want that top end and I have no regrets with the choice. It's all a trade off. There is a reason why the 2867r is the most common choice as people generally hate the stock turbo fall and are chasing the best top end/bottom end balance.