Thanks for the advice, now I think that to do nothing is the cheapest & most effective way to have performance .... chips & cold air intake. I would possibly like to have a little more "growl" by changing out the exhaust system, but I don't need the extra noise. I've had many "kids" come up along side of me & want to drag, ... but being " Cool Hand Luke", I just take off normally & watch them burn rubber, smoking their tires while I smugly move on....kind of a "why bother attitude".

 

You need 20+ additional horsepower before you can even barely feel the difference in these cars. So, if it's the sensation of more power that you're after (other than "halo" effect--imagining something not really present), there's really not much that can be done without spending a lot of money. I'm speaking of internal engine mods, not bolt-on external.

The OEM exhaust system--from cats to tips, while horrible from a performance design standpoint is almost adequate for the naturally aspirated (N/A) cars and there is little to be gained. We did get a few more ponies and about 20 more ft.lbs. of torque with the MacLeod Performance Mk II X-Pipe on N/A cars. Nothing to write home about. Of course the sound made one think there had to be 50 more horses under the hood! :-)

The free flow intake system I built, in conjunction with the Mk II X-Pipe, seemed to add another 10 to 15 hp, (but not by itself). I don't want to quote exactly because I was never satisfied with the dyno tests as the car being tested had some misfiring at WOT. So, not much to be gained with the best of exhaust & intake mods together on the N/A cars.

The potential for real improvement with the exhaust and intake mods lies with the Supercharged (S/C) cars, not the N/A cars. This based on about 10 years of tuning and developing performance parts for them.

Don't waste your money on chip tuning and other hocus pocus. The Jag programming is very good. All that can be done in the best of circumstances is to alter the air/fuel ratio and ignition timing. I've looked at this very carefully and the factory parameters are excellent while maintaining a reasonable safety margin. Maybe a few more horses could be obtained, but at the considerable risk of doing some damage. Even then, "mail order chips" are almost always worthless, the only way to do it properly is tuning the individual car on the dyno.

If you really want noticeably more power, buy a 4.2 supercharged car. That is the most practical, least expensive, biggest bang for the buck solution.

It also provides a solid platform with stronger engine internals for potentially dangerous amounts of power increases.

My car, a 4.2 S/C, has dyno tested at over 600 rwhp, and there is more available. Frankly, even with all the safety features and a factory SVO suspension, it has reached the point of being dangerous in the hands of any but the most experienced, responsible, cautious drivers.