The 2.0L turbo engine internally known as the LNF has been one of GM's unsung heroes over the past several years. Lying at the heart of the Pontiac Solstice GXP, Saturn Sky Redline and HHR SS, the engine generates a very respectable 260hp and 260lb-ft of torque in factory trim.

But GM's performance parts division decided that just wasn't enough, and through a combination of remapped engine calibration and upgraded MAP sensors, the LNF now puts out 290hp and 340lb-ft of torque in manual-transmission variants of the Sky Redline and Solstice GXP. Automatic versions are limited to 325lb-ft, and the HHR SS tops out at 315lb-ft.

A penalty of upgrading to the higher output from the 2.0L mill is the requirement to use premium fuel. However, the good news is that the kit is 50-state emissions legal and the kit won't void your warranty.

The most enticing aspect of the $650 kit for some, however, is the enabling of the ECU's 'learning' feature, which enables the computer to adapt to and benefit from basic bolt-on mods such as intakes and exhausts. That opens up a whole new world of tuning potential for the LNF cars, as well as packing a huge performance punch for a relatively small price tag. The final benefit of the kit is a slightly raised rev-limit - now 6,500rpm, up 200rpm from stock.

Those with a keen memory will recall the GM Performance Parts enhanced Pontiac Solstice GXP Coupe (pictured) shown off back in November at the SEMA auto show. That car boasted the same Stage 2 upgrade kit, plus some other mods to show what is possible. To revisit that car, read our original coverage here.