help! 360 not running right

Well i filled up my tank last week at Chevron. 15 miles or so later my car started to sound funny. Not sputtering. But a deeper sound. It still has power. I replaced all the plugs with new ones. I thought it might be a coil. So i checked them. I had a bunch i purchase a while back off a guy so i replaced a few coils. Didn't help. I got out my code reader. No codes. I did notice more water than usual coming out of the exhaust when letting idle in the garage. Water does normally come out of exhast but i don't ever remember seeing that much. I guess it could be bad gas. But it came from an incredibly busy Chevon. Any thoughts?? Oh its a gated 99