The SMS Revo (303 hp) and SMS Revo S (375 hp) are two editions built by Schmidt Motorsport (SMS). Revo spawned from the slogan, “it’s not evolution, it’s a revolution” when SMS constructed the Audi S2 coupé.

Unlike other tuners’ offerings, the Revo versions of the first generation S4 & S6 were on offer via dealerships, and cars could be shipped directly from Ingolstadt to Cadolzburg for enhancements.

The Revo meaning the upgrade to 303 hp through a bigger turbo, new air-ways and an adapted engine management, whilst the Revo S at 375 hp was a more complex build – in essence pretty alike what many tuning their Audi would refer to as a RS2-setup with an upgrade to K26 turbo, improved exhaust manifold, upgraded injectors and an adapted engine management to suit.

NB! Someone must gladly correct me:
My impression is that the S4 was offered only as Revo, and it was not until the S6 also the more extensive Revo S-version would be on offer. However, retrofitting would enable the Revo S kit for the both Audi S4 and S6.

Schmidt Motorsport has started their own YouTube-channel, holding a very nice (German) presentation of their Revo S: