my evo8mr 100% stock boost max reach 1.5bar, then stable at 1.3 to 1.4.
after i change the exhaust (de-cat to muffler), boost max reach 1.55, then stable at 1.3 to 1.4.
for o2 sensor, you need to do proper conversion from voltage,
< 14.2 = lean
14.2 = stoich
>14.2 = rich
apexi turbo timer can show the air-fuel reading, but the number keep jumping, not easy to read when driving.
i install K&N air-fuel meter, come with o2 sensor, LED type. narrow band. now got old stock at lower price from speed work (dunno still available or not), you can go check there, about RM600, other places selling above RM800.