will i be safe with this A/F gauge

[Mustanggt108]

after the mongoose instal alone with the "Safe Tune". I was planing on getting this item for A/F
http://www.rpmoutlet.com/aemgauge.htm
will i be safe with Tim's save tune and by checking A/F with this gauge.I mean is it very accurate ?

thx

 

[Dope 97GT]

should be fine also this site has them as well. www.dynotunenitrous.com i bought my wideband O2 from them

 

[Red2000GT]

Ditto