I have a Jag S Type 3.0 2000. I’m not interested in getting a bigger engine model, I was just wondering how I could RELIABLY, add 40-60 more hp without having to swap. I like the 3.0l and I wanna make it a nice “streetable” sleeper that can pull from a roll and zip through traffic when necessary.

 

You can't. No-one does that and it would be HORRIBLY expensive if they did - cheaper to buy a different car.

 

Agreed with JagV8. Sell yours and purchase an STR or possibly a Hellcat????.

 

Your stock engine puts out nearly 1.3 BHP/CID, or 80 HP/Liter. Trying to get more out this engine gets you into the law of diminishing returns (financially) very quickly; also, the pretty much bullet-proof reliability of the engine may well be lost in the process.

 

You can go for a E85 remap, mid silencer removal, sport catalyzer, porting your throttle body + intake manifold. You should open your manifold to clean it at least you'll see how rough it is inside. But you won't get 40hp, maybe something like 20 or 25hp. You can go for bigger injectors but the ones that direct fit are motorbike's injectors (Polaris Victory v92). Very rare to find.

 

Manual gearbox would be the easiest, I guess?

 

Yes if you sell the car and buy a manual car.