MPH go up when i rev while stopped, out of gear M6

[ApexVIII]

so my car started sounding funny today, i have LT stock cat back and a electric cut out.

when i go WOT the tires dont break loose as fast as they have been the exhaust seems to not be as loud, and has alot more rasp to it

like there is a exhaust leak, but when i shut the cut out there is no exhaust leak to be found. there also is a squeak that happens right be for red line at WOT
any ideas?

scanned it here are the codes... my SES light has been on ever sence i bought the car lol its not tuned for the headers..

but

P0153
P0133
P0134
P1133
P1153

[rsg98Z28]

dont worry about the mph gauge my car does it too and i also have afreind with a 98 1500 his does the same thing as for the rest i will have to give some thought

[Tyler_LS1]

My Camaro doesn't do it but my Chevy K2500 does..

I dont think its a problem, it accurate according to GPS

[ApexVIII]

My Camaro doesn't do it but my Chevy K2500 does..

I dont think its a problem, it accurate according to GPS

oh lol ok thats good to know

Thanks alot guys,

i wonder why my car started making the weird sounds hmm ill have to scan it and see if there is anything

[0rion]

any unusual ticks? Could be an exhaust leak that's not showing itself until you go WOT. How many miles on your O2 sensors? Notice an unusual amount of soot in the exhaust tips? Just ideas. It could be a ton of things. Start simple and cheap.

[ApexVIII]

any unusual ticks? Could be an exhaust leak that's not showing itself until you go WOT. How many miles on your O2 sensors? Notice an unusual amount of soot in the exhaust tips? Just ideas. It could be a ton of things. Start simple and cheap.

yea, lol the rear two o2's are not even there lol they are bypassed.

i replaced the passesngers side one about 2k miles ago. but the odd think that makes me think its not a exhaust leak even though it really sounds like one is,
that it sounds bone stock with the cut out shut then when i open it thats when i hear the raspy/exhaust leak sound. the car does also feel weaker too.

not really any weird noises other then the squeak at WOT and the exhaust noise