Boost - you need this to set your boost level

EGT- can warn you of iminent meltdown and high egt's are seen in too lean or too rich of a tune

Water temp much more important in warning you of problems then oil temp imo if the water temp is into the red- everything else tends to be.

A/f is good for tuning if you have a uego wideband but they are expensive and the sensors burn up- i have killed 2 already. On the otherhand, narrowband a/f gauges are pretty useless.

 

would you need sensors or anything else if you bought greddy electronic boost, oil pres., or egt gauges? also, what if you bought a greddy turbo timer or e-manage...would you have to buy sensors or electrical harnesses for them?