^Pretty sure you're referring to me lol.
I have the EFR 7670 with two Tial 38mm external gates, one on each runner, with a short runner manifold. I had the runners built as short as possible out of 321 stainless. This turbo has RIDICULOUS spool. Mine starts around 2k rpm, and I'd say reaching full boost by about 3300-3500. The problem is I haven't been on an actual dyno yet to get any info, and I've had this turbo on since early last year. It also sounds like a jet engine, but that's just an added bonus lol. Anyway, the only thing I've done is virtual dyno, and I'm not sure how much stock I put in that. Supposedly it's within 5% accurate, but having not been on an actual dyno yet, I couldn't tell you for sure. And since all dynos read differently, I'm not sure it would make much difference anyway. All I know is if you want response similar to stock twins but more top end, the 7670 is perfect. I can't speak to the 8374, but I was thinking of possibly stepping up to that one next time. I wouldn't say for sure you can't break 400whp with the 7670. I'm at 6000 ft altitude and I'm already pretty close to 400 (according to the virtual dyno anyway), and we lose quite a bit of HP up here. Although the spool is so fast and strong that I have to turn down the duty cycle on the boost controller in the first couple gears, and a little in third gear, or I'll spin all the way through. That's why I was thinking about going with the 8374 next time. I imagine it spools just not quite as fast but probably pretty close, but will still get you more whp. Here are some pics of the when I was installing everything.
