A4 misfiring please help

[thegasman2000]

I have a 99 audi a4 1.8 it has satrted misfiring and is terrible to start when driving it it is as if something is holdiong it back, ive changed the coil pack at great expense. although it runs better its as if its flooding when i really strech its legs and wont rev over 4500. any suggestions any one :(

[gregpaterson]

if you ran it for too long with a misfire you could have damaged the cat

[thegasman2000]

ive changed the air flow sensor now and it does rev properly there was also a small pipe on the top of the engine which when i touched it the car cut out so ive changed that. would a damaged cat cause it to still backfire slightly ??? thank s for helping

[gregpaterson]

it might but are you sure its a slight misfire and not just extra exhaust noise

[Dave Avant]

Its always difficult to diagnose on t'internet as some describe a slightly blowing exhaust as sounding like a misfire.

As Greg says, has it been misfiring long? Misfires can 'melt' cats blocking them, when they block albeit partially it won't rev properly and it will feel strangled. Did you change the plugs aswell?

What was the pipe, can you take a pic?