rx8duder55

2004 RX8, 72,xxx miles w/P0455 (gross leak) and P2096 codes found with my OBDII reader and Torque pro app.

Spark plugs have failed twice in it's life, 1st time due to accidental overfill of oil, which resulted in some "head gasket like" smoke coming out the tail pipe symptoms. Plugs failed again in the fall of 2012, had been about 35,000 miles, so due to replace anyways.

Car is currently experiencing symptoms of delayed acceleration and power loss after extended periods of driving on the freeway (30min-1hr). Symptoms do not fully subside until the car is allowed to completely cool down. Very noticeable whooshing/whirring noise during acceleration after the car has been driven for extended periods of time. The only other time I have noticed this noise is when the car is cold. Otherwise it seems fine around town.

Due to symptoms, I am unsure of what these codes might mean. I have replaced the gas cap as a precaution, but I am thinking I might have a faulty catalytic converter due to my former plug failures, not to mention I may have a solenoid valve problem since my car continually throws P0455 (gross leak) codes at me even after replacing the cap. Other options I have ran through are a possible exhaust leak (whooshing/whirring noise?) but I am unsure.

I will get underneath the car in 2 weeks time (March 23, 2013) to install an aftermarket exhaust and hi-flow cat pipe (turboxs), and will see what happens to symptoms. Thankfully this was a planned upgrade I decided to do sooner to see if this would fix my problem. If it does not help it will only serve to help me further narrow down what the problem may be.

Any knowledge or wisdom on this delayed acceleration/loss of power after driving for prolonged periods would be much appreciated in the meantime! I have scoured forums and can't seem to find much about this issue.

Thanks in advance.