For years, Florida's RENNtech has long been the first stop for well-heeled Mercedes mavens and prospective road-rallyists who wanted an output boost for their SLs. But the company offers hi-po gear across the Merc range, from the lowly (not to us) Sprinter to the highbrow SLR. The SLR too? Right. Upgrades to the pride of Mercedes-McLaren 722 take the form of upgraded intercoolers and their respective pumps, allowing for more boost and putting the 722 (named after Stirling Moss's and Denis Jenkinson's starting time in the 1955 Mille Miglia of 7:22 am) closer to 722 horsepower. As for price, consult your tax accountant.

RENNtech's 722HP Mercedes-McLaren SLR 722 [Motor Authority]

More on the SLR-Powered Mercedes SLK: Out of the Mouths of Mechanics [internal]