Stock, my 2013 made 391 rwhp and 378 rwtq. You don't think a stock upper intake can support a gain of less than 50 rwhp and tq?
Shoot, even my 2007 4.6L went from 265 rwhp and 235 rwtq to 308 rwhp and 295 rwtq with a CAI, full exhaust (including American Racing LT's) and a tune. And both cars were tuned by 2 different guys on two different dyno's, yielding about the same results.
I hope I don't come off like a "know-it-all" lol, however I know the stock intake won't support that, it's why most people switch to the boss intake when they're NA. Porting the stock manifold doesn't gain anything either. I've seen "dyno racers" switch to the Boss intake just to hit the 420rwhp mark.
If your car dyno'd 391rwhp stock, that means you have roughly a 7% drivetrain loss, which just isn't happening with a stock driveline.
For reference, my coyote made 456rwhp/400rwtq (Dynojet/SAE corrected) with a ported Cobra Jet manifold, 147mm Monoblade throttle body, FRPP CAI, long tube headers, and O/R H-pipe. I'm running E85 as well. Max effort NA coyote builds barely make more than 425rwtq, certainly a simple bolt-on coyote won't see that torque on a calibrated dyno.
Dyno numbers are for the birds anyway, ETs and trap speeds tell the real story. Dynos are just tuning tools, too many discrepancies between them to rely on HP numbers, IMO.
With that said, I'd stick with the stock intake if the engine won't be spun passed 7000+rpm.
Sorry for writing a novel right here lol
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