What is the best way to increase engine performance to gain a little more horsepower and torque: K&N Air Filter, Entire Air Intake Uprade or complete Exhaust System Upgrade to SS? I have a 2003 DSII.

 

There are none that are cost effective.
K&N will kill your MAF, air intake will not doing anything for you but let in a lot of hot air, except at highway speeds where you will pick up a 1/4 MPG and the exhaust, on the road, maybe 1/2 MPG. Just to rule them out, forget chipping the engine, you'll just burn more gas.
What have you done so far, how many miles on your truck and what octane gas are you burning?

 

Depends where you want of your engine and what your local legislation will allow you. Within those two realities, the possibilities are endless, with the only restriction being your pocket book and the need for reliablity. Answer the 'want" and the "legislation" questions and the rest is easy.

Of course, the level of expertise and resources is very low in the US. The vehicle was made elsewhere and never developed an extensive local aftermarket for happy improvements. (Which is sad as the US normally has the best automobile aftermarket in the world). On the other hand, expertise and support are very high in the UK and Australia, and their mods are tested, far more effective and cheaper.

James

 

Yes, but not here.
An 03 has more then enough power and can only be improved on with big bucks, Head work, cam, header and exhaust all together.

 

Check http://www.rpiv8.com/

Power is only limited by the money you want to spend or don't.
You can call and they can let you know what will work for a 03.
They are 6 hrs ahead of central time zone, talk to Lisa.

 

if you want a few more horses, swap your crank sensor wires, itll advance ign timing 3 degrees, and you must run 93, but you should get a noticable difference

 

will swapping the crank sensor wires work on a 97 4.0 p38? Ive never heard ot any one doing this.

 

hey, i put a single 3 inch exhuast 2 into 1 got rid of the catalitic converter put a single turbo mufler,i run some thing very similar to a k&n but it doesn`t have the oils to disturb the maf,its a throw away thing. andrun a simple cold air induction system which is cheap and easy to do, i also run a minimum of 95 octane, i`ve increased power from est 105 kw to 120kw and it gives me rughly 80 klms extra per tank should be more but i drive the truck hard because it sounds soo good,with no mayjor engine mods.And my truck has done 300,000 klm

 

What year is your truck.
Here is the states, we can't remove our cats, the ECU will go into open loop and the engine will run way too rich.
Doing the other stuff you did is good, you might want to consider having the heads rebuilt, ported and the chambers enlarged for better air flow/ more power.

 

Swapping for a slightly taller Crower cam is VERY effective for improving performance.

I have only done "Desktop Dyno" testing, but the performance increases were impressive on the computer screen and in the truck.

I'm not sold on head work due to the need for low end power off-road. Headers may be effective, but will require complete exhaust replacement to get the full benefit.

Megasquirt (or other field-tunable EMS) may hold some promise, I don't know yet, the plate's way too full to even think about it.