[Southcross]

heated fuel yes...

I suspect though, if you tried to lean out your injector pump your EGTs would go through the roof and cook your turbo. I'm gonna say no, unless you wanted to invest in watermethanol injection/etc to bring them back down.

What kind of vehicle? On the VW TDI engines, you can chip them... while it gives the engine more power/performance, if you keep your foot off it (drive it normal, hypermile would probably make a huge difference), its been reported to increase efficency by 5-10% (hypermiling would likely do even more) due to better timing and mixture.

If I had to guess, without knowing your engine/enginemanagement... timing, timing will have the greatest single effect you can do without external modifications (chip, water-meth, etc)