I posted this same problem on Saturday. Flowmasters came with my 98 Z28 - coincidence? ANYWAY, I read and checked out the search here and decided to drive my Z28 on a long roadtrip to Omaha, about 120 miles. After a few punches of up to 110 on the I-80 and about 100 miles the SES Light went OUT. Drove around town, stopped a few times, checked to see if the SES Light would illuminate with the key in, ALL IS good now. The Camaro manual actually tells you to do this. So do others in here. By the way I got 297.4 miles on that tank of gas, BAD GAS??? Took 13.58 gallons.

 

Flowmaster or flowmasters?

and what does a muffler have to do with you SES light?

 

I thought the Catalytic converters could cause SES light to come on, I'm not a know it all like yourself so I wonderd if the Flowmaster exhaust had something to do with my CAT's. Look, all I wanted to let the other guy know was this worked for me. I think I got some bad gas and it ran out after 120 miles = No SES.
I ahve NO idea what kind of Flowmaster setup I have neither did the dealer when he looked at it. There is no mufflers there, I can see that. Bought the car like that and it has a Flowmaster sticker on the window and on the K&N FIPK lid.

 

Uhmmm

Your post just wasnt very clear