joshuaho96

A remap is not magic, it will not solve your idle issues. Any GTS-T ECU will not be compatible with an NA motor, the timing curves are completely different due to differing compression ratios. An RB25DE makes about as much power as a modern economy car, the only way to change that appreciably is forced induction. Or if your engine is really in bad shape and needs a rebuild.

This is pretty much it. I would also make sure that your grounds are properly set up, if you used stock harness and PnP adapter for the ECU you should not have problems but any noise on the coil trigger will cause spark to go off continuously which will manifest as a no-start condition. You should also verify power to all components like ECU, ignitor, etc are sufficient during cranking. Some ECUs are exceptionally finicky about power supply and will lose ignition sync, etc when when cranking pulls the battery voltage too low.

A proper tune will never take ~3-4 hours unless your tuner already has a canned map, your car is perfect, and they just need to verify that everything is running properly + maybe small tweaks here and there. It will take a few days to do it right even though Link or whatever ECU manufacturer of choice is providing the base map which shouldn't be too far off in the first place. OEMs take months of engineering time to do the factory calibration. It's a full time job. Even then sometimes they run out of time and it's too late to get another calibration emissions certified and you end up with a factory tune that breaks engines. Subaru has done this before. With a turbo engine especially the dyno cannot do everything for you, some road testing is needed to tune for real-world IATs. Engine calibration is not for kids. If you don't trust your tuner to not crash/abuse your car they have no business doing an ECU calibration. Some logging is needed to diagnose why your car is running wrong on the base map, if you can screenshot a trace of the behavior people can probably help.