Are you really in John O'Groats ? If so then Hi
HP and Torque are the same thing really.
Mr Duckworth (the "worth" in "Cosworth") expressed HP as "size of bang multiplied by number of bangs". So think of "size of bang" being the same as torque. To improve that you will need to :
- Increase the amount of air in the cylinder (so you can efficiently burn more fuel)
- Decrease the temperature of the air in the cylinder (so it is more dense, and you can efficiently burn more fuel)
- Reduce parasitic energy losses such as the energy required to fill a cylinder on the induction stroke and the energy required to empty a cylinder of exhaust gasses.
- EDIT - Reduce electrical load. No A/C, LED lights etc.
Yours being the "truck" engine doesn't have any other clever trickery such as VVT or multi valve heads - it is designed for reliable "slogger" torque and as little looking after as needed.
Your new exhaust
may give you the latter option but even then the effect is going to be blunted by the rest of the induction / exhaust system - the valves, head ports, manifold etc. I suspect all you will have is a rust proof exhaust and a rather annoying "moooooooooooooooooooo" noise as you plod along, and nothing else.
You may be able to decrease the temps with a CAI and an air filter but probably not as, again, the rest of the induction/FI system will bring temps back to more or less what they were before without lots of work. Been there, done that.
If you really want to increase torque I would ponder forced induction of some kind - more air squeezed in, more fuel burned and a bigger bang when you need it.
Also (I've suggested this on other threads but...) maybe a swap to a Diesel motor (there was a 2.4D in the Hilux here) or better still a TD would be preferrable but that depends on how cheap they are where you are, the cost of conversion (not forgetting gearing) and how long you want to keep the vehicle.