MP39 is... Sunstreaker!

[Magnus]

The black struts are there, it's just that the spoiler is yellow. And as Magnus and I have both mentioned before, it's likely to do with a condition of licensing with Lamborghini. The clear scans provided in the link by FatalityPitt confirms that this toy does have a licensed vehicle mode.

The trademarks copyrights and design rights in and associated with Lamborghini, Lamborghini with Bull and Shield Device, are used under licence from Automobili Lamborghini S.p.A.

Lamborghini's influence is confirmed in a translation of the design team interview page:

With the development of this Masterpiece, Lamborghini was very vocal in the lead for alt mode design cues, which is the opposite way to tackle a design such as Sunstreaker, however, we have a relationship where were able to add alt mode styling, gimmicks, and a cartoon likeness.

There was also a desire to maintain that accuracy to the original Countach because MP Sideswipe also appealed to car enthusiasts:

The popularity of MP 12 Lambor was a success amongst not only Transformers fans but also car enthusiasts. We decided we could not completely ignore the desires and wishes of the car enthusiasts.

I wanted to present Sunstreaker as a product that Countach fans would recognize while taking advantage of his animation styling.

As I posted before, I'm glad they took this approach.

The taillights appear to be a permanent fixture which are covered up in the "Super Tuning" variant transformation.

Yes, the toy was designed as capable of appearing as both stock and modded Countach without adding parts:

I tried to reproduce both the animation & real car alt mode design in a way were the transformation is incorporated instead of making him partsform.

Its a situation providing the best of both worlds, we even made the doors open.

I'm not particularly attached to or a big fan of the Sunstreaker character, but this figure looks too interesting to pass up.