Something is wrong if your high amp charger doesn't work with any device (and with your device in particular).
Yes - it's well known that some GPS apps can use more power than a charger can provide - drawing down the battery over time. I have seen the battery drain about 10% to 20% capacity an hour when everything is operating properly.
If your drain is higher than that, then perhaps the phone needs to be restored or there is some problem with the charger. Have you sent the developer a support request to see if you can use a setting to slow down the CPU if it turns out to be a software issue?
Basically, it depends on how much a deficit your device is running to know what to blame in your instance, but you could test things by enabling the detailed charge indication and testing how long it takes to go from full to 75% charge. Both in the car and in your house connected to the Apple AC adapter.
If the car charger isn't keeping up with the wall adapter, then you can replace that. If it's draining equally at home, then it's either the device or the software.