Q: How to get more horsepower without the check engine light and still still pass smog

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Looking to increase horsepower to 250 but when I researched putting new headers on the car, said I would get a check engine light code P0420 that forums say I would need to change out the catalytic converter? So, I'm looking for the expert professional advice for gaining the horsepower.

My car has 206178 miles.
My car has an automatic transmission.

Coming from a realistic point of view, I’d say that unless you were to pull your motor and completely rebuild it, from pan to fuel injection, you might want to consider NOT adding components for horsepower. With over 200,000 miles, connecting rods, cylinder head hardware and bearings are probably running thin as it is. Adding HP adders, like performance chips for ignition, exhaust components or custom intake manifolds could end up shortening the lifespan of your motor. One newer part you might want to consider however that actually helps to improve fuel efficiency and power is the Phoenix Fuel Converter. I worked with these guys for a while, and can testify to how well it works to improve fuel economy and throttle response. Plus, if it’s good enough for Chip Foose, it’s probably pretty reliable.

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