It seems to me that the air/fuel gauge is slightly less necessary during the very beginning stages of modification... I would think it would be best to start out by keeping an eye on things that could slowly increase or decrease to a point of destruction (like pressure or temperature) to make sure you don't reach this point instead of watching a gauge that constantly changes when you drive like the air/fuel gauge (I guess the boost gauge is similar to this, but you can still sort of keep an eye on it when you hit your max boost to make sure it doesn't go too high). Maybe I am completely wrong, but from what I gather, the air/fuel gauge becomes more necessary during later stages of modification when you start tweaking specific parameters of the ecu with more hardcore tuning software (UTEC? enginuity?) and want to observe patterns or data log exactly how your engine is running... please correct me if I'm wrong because I'm still trying to learn this stuff.
07 WRX (Albins 5MT + Blouch 20G)
Jorge Carrillo Tuned (365 whp/340 wtq)