Here are some observations I made from my research.
1. Go to a guy who knows what he is doing & won't brick your ECU.
2. Never allow the tuner to remap such that you are producing more than 6psi boost under 1500rpm. This is the key to a reliable engine. What most ppl try to do is map for more boost at lower rpm not realizing that this will cause something known as "compressor surge" & destroy your turbo.
3. Never exceed more than 4psi over your OE turbo boost. If your turbo is running at 15psi stock, stick to 19psi max.
4. Care has to be taken not to increase injection timing/rail pressure/boost by too much.
5. Raising the injection timing by too much increases the peak cylinder pressure by about 15% and shoots up the piston temperatures thru the roof with just a 2 degree advance.
6. Make sure there are no boost spikes happening.
7. Always keep an eye on your EGTs to avoid damages to the engine.
8. If you are upgrading injectors, make sure to find out if your rail can supply fuel at recommended pressure.
9. Change engine oil & air filters regularly.
10. Make sure your tuner us using legal paid software. Often most ECUs are bricked by guys using free cracked software.
More when I recollect....
11. Find out the engine & gearbox code and find out what is the max torque that is being put out on the same combination. It's safe to assume that you can try to achieve 20% more torque on the highest figure given out ny a manufacturer without losing reliability by too much.
Anything more, would mean your clutch will give up. Then come issues like busted gearboxes & engine internals.
12. Always save a copy of your base OE map.
PS: Can one of the mods merge my posts?