Anyone know of any mods I can do to my 4.0L? Dont bother telling me I should get the STR 4.2, If I could... I would, Where I live it would cost me my arms and legs to get one. So simply what can I do to upgrade my 4.0 Stype. Anything and everything.

As of now I have done after
(9" Ford Rear end)
(K&N Cold air intake)

Anything related to exhaust or the computer system that may give it a bit more power?

 

Changed the timing chain tensioners? If not, engine is on borrowed time.

 

Jagv8 is right , get those cam covers off to determine its done or not before anything else !
Or the money you spend may be in vain !
No one wants an s type yard ornament with a k&n fitted!

So realy there isn't mutch to gain with mods it's already near $300hp,
But high flow cats , k&n , cold air , cat back exhaust , and possably a tune if you have someone near by that is capable should make a small but noticable gain !
Don't bother with eBay chip tunes ! I think paramount has a generic remap if you send them your ecm , but not certain they have one for 4.0 na !
Go to this link and fill in the questioner to see if your model is covered .

https://www.paramount-performance.com/ECU-Tuning.html

As far as I've heard the gains for the remap on the sc cars are not great value for money results !

Or buy an aftermarket ems like link , wolf , motec , microtech , heltech , motronc or apexi!
Throw one or two turbos on and tune your little hart out !

 

The K&N cold air intake netted, at best, zero power increase or it may have lost you some if it's like most of them seen here.

Gains from an exhaust mod will be minimal. Forget aftermarket ECU mods. No one has developed anything worthwhile.

Dollar for dollar, the cheapest way to get substantially more power is a Type-R.

 

Alright so it seems I drive it until it crashes, let insurance pay me out and import a STR. That way I still have the jaguar luxury and the lovely speed with it. Thanks for all and any advice you guys gave me!

 

You'd get more for your present car by selling it privately than an insurance payout. No need to import a Type-R, there's some available already in Canada. One right next door to you in Edmonton

2003 Jaguar S-Type R for $11,900 in EDMONTON | autoTRADER.ca

Not a bad price.