Why is the 2013 GT 4cyc 158HP and all other models 167hp

Where did you get your info? Im not shure but there may be a HP difference between the manual and auto trans.

Edmunds shows the GT at 167HP @ 7000rpm. Heres all the specs: http://www.edmunds.com/mazda/mx-5-miata/2013/features-specs.html?style=200438625

With the Auto Trans. model MX-5, you pay a HP "penalty", likely due to the weight of the Auto Trans itself and it has 158 HP...The Manual Transmission model (whether it has the Retractable Hardtop or not) is 167 HP. Highly recommend that you get the 6 speed Manual...I've got a 2011 MX-5 GT w/Retractable Hardtop and MT....The car isn't nearly as much fun and you can't "work" that engine with the AT slushbox!

That's only a drop of 9 HP under the 167 HP of the manual tranny. Personally, I use my auto trans in the manual mode and find it to better than the Mercedes transmission found in the older SLK and the Crossfire coupe and roadster, both of which I have owned and loved. The manual mode gives me better gas mileage as well as superior performance, coupled with the ICU tuning and DYNO-Tune it is still 24 HP greater than stock. My car is a 2007 Touring model with the retractable Hardtop in Highland green.

Just added a photo of my car.

Good looking MX-5 @ mighymini11 :) You should post of pic of her in your CarGurus Garage though! I have a co-worker with a really nice 2008 MX-5 Grand Touring w/retractable hardtop and AT in Jet Black (Been trying to convince her to drive home with the top down more often...She's too worried about her hair...told her to just brush/comb it when she gets home ...yeesh!...LOL!)....I've tried to use the Manual Shift mode in the AT in my 2nd vehicle, a 2010 Mitsu Outlander SUV (and on my GF's previous car, a '03 Mitsu Eclipse)..and find it challenging to get the shifts timed right...I like it best for Engine Braking..slows it down nicely when I see that State Trooper ahead! Also, Manual mode gives my 4 cylinder SUV a little extra "ummph" in 1st gear from a dead stop.

Here's my MX-5 :)

Will do, thanks