i cant seem to figure out why my 1995 t100 is making this noise through the exhaust its only at idle when warmed up. the idle was low at 550 rpm when warm but i bumped it up to 750. It has newer plugs and wires a new fuel filter and i just flushed the coolant, I also ran seafoam through it. has 185k well maintained. I just recently had a magnaflow muffler installed and I don't think it made the noise before I just noticed it one day when I was letting it warmup. I don't know if those mufflers "break in" at all but it's gotten louder since it was installed could it be because less back pressure? has no codes stored. any ideas guys?

 

More then likely you just notice it more because the muffler is louder then your old one.

Some mufflers are just made better saying just Magnaflow without a model is like saying I drive a Toyota and leaving it at that

 

all i know is its a magnaflow knock off, it was what the muffler shop carried.