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A 996-generation Porsche 911 Carrera 4S Cabriolet isn't hard to find. One with a six-speed manual and the factory X51 Power Kit is a much shorter list, and a Seal Grey example is live on Collecting Cars with a week left on the clock.
What X51 Actually Is
X51 was a factory engine option for the 3.6-liter 996.2 Carrera models, offered from the 2003 model year. It lifted the flat-six from 320 horsepower to 345, according to Elferspot's 996 breakdown, while peak torque stayed at 370 Nm. RM Sotheby's, which has offered an X51 Carrera 4S Cabriolet of its own, describes the kit as revised intake and exhaust manifolds, reworked cylinder heads, and different camshafts and valves. It wasn't a dealer add-on. It left Zuffenhausen that way.
It also wasn't common on the cabriolets. RM put 2004 Carrera 4S Cabriolet production at 4,543 cars and called the X51 ones a small number of them. Porsche didn't publish a clean take rate, so nobody can give you an exact count, but pairing X51 with the 4S's wide body, all-wheel drive and a manual gearbox is a combination you have to go looking for.
The Rest of the Spec
This car pairs the X51 engine with a six-speed manual and the 4S's widebody shell, finished in Seal Grey over black. It rides on 18-inch GT3 wheels with red calipers and has the XLF sports exhaust, bi-xenon lighting, a Bose system and the PCM 2 infotainment unit. The factory hardtop comes with it. The odometer reads 71,740 miles, and the seller has owned it for more than nine years.
The listing calls it a 2006 model, and it was first registered in July 2006. The VIN's model-year character is a 5, which decodes to 2005, so this is better read as a late-registered car at the very end of 996 production. The seller notes the C4S generally stopped being built in 2005.
What to Weigh Before Bidding
Not everything here is original. The seats have been retrimmed in Daytona Red nappa leather, and the heated memory front seats came from a Porsche 996 interior upgrade. That's a matter of taste, but it matters if you want an untouched factory car. On the mechanical side, the listing says an EPS IMS roller bearing upgrade has been fitted, a recent borescope inspection reported no bore scoring, and the service history shows the gearbox came off in October 2023 to replace the IMS flange seal. As always, descriptions are the seller's own, and the listing points buyers to the 151-photo gallery and MOT history.
If you're still sizing up the 996, our Porsche 911 996 buying guide is a good primer, and the 996 Mezger market shows how far the Turbos have run ahead. For an open-top Porsche from the generation before, see this 1989 Carrera Cabriolet with the G50 five-speed.
The bid sits at £10,000 as of this writing, and the auction ends on November 10 at 2:20 p.m. ET. The car is in Warrington, UK, and is right-hand drive.
