sorry bout the stupid question but ...

just curious, how do u know if u might have bad compression ?
sometimes my car lags around 3500-4000 rpm
i thought it might be bad plugs or wires ?
also, when i downshift hard, mad smoke comes out of my exhaust
my cel light was on for a while, but i thought it was a bad cat

are these bad compression symptoms ?
the car runs strong otherwise ...
i want to know if these are the right symptoms
if it is ill get it checked out

 

gonna need more info. Like year/make/model.

 

00 em1 if it helps ? 85k on the odometer
i have i/h/e with an aftermarket cat and b&m fuel regulator

 

do a compression check to check if there is not enough compression

any shop can do it, even pep-boys.

 

i know i can get it checked out ... i probably will
but i just want to know the symptoms of bad compression ... ?
i dont want to waste my time if none of the problems i have are related to compression problems