as already stated, dont waste your money. you got some bad info. anyone feel free to correct me if im wrong. I managed a parts store for a long time, I know a lot of these aftermarket products.
#1 Replace the Cold Air Intake – K&N Air System (@ $300) – Apparently an easy fix that you can do yourself
You can only replace the filter, no such cold air for these beasts. As said before, already built in. A filter will cost you about $65 but will not gain you any performance. It is a better overall filter, but no performance gained.
#2 Replace the exhaust system with a Barla or Dynaflow (cheaper) system (@ $300 to $500). This would have to be done by a shop. Range Rover puts in a super heavy system that puts a lot of back pressure on your engine.
Borla does not currently have a system available, nothing that bolts up at least. Dynaflow is a type a muffler that Banks Diesel makes. They do have exhaust's, but nothing for the LR3. Magnaflow and Dynomax are two big companies, but neither recognize the LR3. Look to a dealer overseas, that's about the only place to get anything worthwhile to bolt on.
#3 Put in a Computer Chip to calibrate the system. (@$50 to $500 at any auto parts store). This is the last thing to do as the other two will affect what the chip reads. This you can put in yourself.
You might as well sign the life of your LR3 away. There is no such piggyback style chip for this motor. You can get the one on ebay for $25, but from my experience the hyperdrive is broken and you wont be able to reach lightspeed. Overseas diesels only for computer upgrades.
My recommendations for fuel. Check tire pressure regularaly. Use good gasoline, this can be argued forever but I noticed good gains with large refinery fuels. Stay away from gas stations that have no branding and constantly buy from the cheapest bidder. Stick to the refineries like Sunoco, Lukoil, or BP. Use Cruise control when you can. Dont hammer down on the pedal, youll save a good amount of fuel by driving a little more conservatively during city driving.
I only get about 13-14 mpg, so 16 is not so shabby.