its gonna be a hassle and a half to get them changed from this guy.
its only a difference of 121 lbs spread over 4 tires i think i'll be ok
if i die, you guys can chime in and say "i told you so"

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In the US:
Mazda only spec's 91 load rating for 16" tires on the 6i. For 17" and 18", the load rating spec is 93.
Load tables ( 88, 91, 93 ..) are based on 35 psi for most standard (sl) tires, and 41 psi for xl tires. If your pressure is less than these values, reduce the load rating by about 20 lbs per psi.
Load spec is based on front GVWR, which includes load dynamics and is 2361 lbs (both i and s). It is suggested that you go 10% over, so the design load per front wheel is
1298 lbs.
The 16" 91 tires, at mazda's 32 psi, have a net 1296 lb rating.
The 17" 93 tires, at 32 psi, net out at 1373 lbs.
The 18" 93 tires, at mazda's 35 psi, rate at 1433 lbs.
Any standard 88 tire rates at 1235 lbs at 35 psi.
So although you are just 63 lbs underrated per tire with your 88's based on GVWR, you are about 200 lbs below Mazda's spec for 18" tires.
But join the club. Mazda used 93-xl 17" michelin's on the mazda6, and said use 32 psi. That downgrades the 93 rating at 41 psi to 1253 lbs at 32 psi. Don't know if they used xl's for the 18" wheels.
So you are well below Mazda's suggested capacity rating of 1433 lbs for 18" tires, and increasing pressure will not increase capacity on SL type tires.
I'd still just bump them up to 36-37 psi, and not do high speed track events.