I have a tuned PCM from MadZ28.com and I have already removed EGR, AIR, and cats, and I think I may have picked to de-activate the EVAP charcoal system as well. My question is this, how bad does it affect gas mileage and can it cause a miss or slight hesitation at high RPM's? It has been a few months since the install of the PCM, and it seems like recently my mileage is starting to get around 200 miles per tank. I also have developed a slight miss up top. I am thinking that it is probably an opti problem since it has about 80-90k on it and is about 4 years old.

Basically I just want to know if I need to re-activate the EVAP charcoal system and replace it or if I should not worry about it and just replace the opti, because it probably needs it anyway?

 

I doubt it's your EVAP system; this system is used to absorb fuel fumes when the engine is shut off so they don't polute, then reburns them when the engine is running...minimal fuel involved here.

I would look at your spark plugs and spark plug wires as the source of your miss. The opti is possible but always start with the simple things first.

 

Just recently did new MSD wires and NGK TR55 plugs, so must be the opti I assume?

 

Take a close look at the wires with the car idling in the dark to see if you have any arcing. Also look carefully around the coil/coil wire.