[Nixer]

but some tuners change the btld key, esys won't be able to erase the old btld and flash the stock one's.

In that case, if I don't have access to MHD flasher, what are my options?

[bmchicago]

if someone helped you previously flash the DME, most likely they reflashed the DME including the bootloader and internal flash memory after flashing the DME with e-sys the flash memory is factory now. The d-flash or eeprom of the DME may contain flash counters as well as manipulation data, however this would not cause engine malfunction or loss of power.

[Nixer]

I don't have DTM warning or any fault codes indication engine malfunction. I definitely can feel the power loss and there is no acceleration even with WOT. The engine rpm drops to ~1000 as soon as the car shifts to 3rd gear or hit 15 mph or so. Makes absolutely no sense whatsoever.