Header question

I have a 93' Grand Marquis with a 4.8L SOHC engine..... I was recently reading a artical about using the 4.8L engine from a Mustang GT and producing 301 hp by upgrading the cam and putting on full length headers.....
anyway if I do decide to put headers on this merc... how do I by pass the o2 sensors so my check engine light won't come on? This car has a 4 cat system

I assume you mean 4.6L.....

the 93's were a little dumber than newer-OBD2 systems, so it might be possible to fool the O2's compared to newer systems, but as a general rule, there is no "good" method for that. You're better off getting high flow cat's and keeping the O2s. You can pick them up for little money, and there is no performance disadvantages, so there is little issue with going that route IMO whether you are anti-emissions or not

Thanks for the reply and yes it is a 4.6... If I replace the 90 degree throttle body with a straight one (75mm) would I see any significant power gain? Also would a K+n intake that originally fits a 93 Cougar fit this car (it has the same size engine) The parts number is 57-2505-1

Look at K&N's catalogue. I think they offer an air filter for the Marquis. Unless the part # is the same, the Cougar filter is different and will not fit.
Chances are the Cougar air box is different due to different packaging concerns under the hood.

As for the Mustang engine, I believe it's a DOHC version of the engine and is quite different than the SOHC version in the Marquis. It can be swapped in but a donor engine will be pretty expensive.

I'm actually looking for the cold air intake for this car and I did look at the K+N book I have at home but it doesn't have any intakes for the Marquis.....