Isuzu Amigo 2.6 ‘94 More Power

Basically comes down to how much skill and access to parts you have, if you can do the work yourself it changes the cost dramatically....You can go several ways, but first you want to define your goals clearly, more power and torque is fairly vague....an engine swap, adding turbo charger, or just changing the exhaust, how much more do you want?

http://pages.suddenlink.net/wayne/Main/Vehicle/Isuzu_FAQ.htm

https://forum.planetisuzoo.com/viewtopic.php?t=37318

...", the single best power upgrade you can make on the 2.6L is to have the ECM re-chipped. I have heard that Jet Chips in CA"...

https://www.automobile-catalog.com/make/isuzu/amigo_1gen/amigo_1gen/1994.html

https://www.automobile-catalog.com/curve/1994/1263440/isuzu_amigo_s_4x2_2_6l.html

...as you can see the engine is already geared for low end torque....if it's a 4x4 you could remove the front driveshaft to eliminate power transmission loss, but you would also lose some traction....you could go to a shorter axle gear, I think this has around 4.53 stock, but I think there is a 5.33 option....that would lower top speed but increase lower end torque....you could go with a smaller wheel size, this would have the same effect...bear in mind that changing the final drive ratio effects the speedometer accuracy as well, and needs to be corrected....

I would take it to a dyno testing facility to get a baseline performance reading, to see how far from spec you are....you might just need a rebuild....or maybe you just need a tune-up....

"Costs to Tune a Car. Taking your car to a dyno tuning garage is the best way to not only improve performance, boost horsepower, and make the engine run more efficiently. However, initial costs can start at $400 to $700.Oct 7, 2013 "

http://www.autos.com/aftermarket-parts/how-much-should-you-spend-on-a-dyno-tune

<...get more power and torque in lower rpm...> Change the engine for a hurking-great diesel?

<...What I can do...> The forum is on no position to assess the skills of its individual contributors, especially from a post with only a single sentence of information. If that's all that is available for the assessment, the consensus answer at this stage might be "very little".