Reverting to IS12 from IS20

[ahmodity]

So I have a B8.5 1.8T A4 ( CVT ) Then I drove it this morning the EPC warning came on + a warning of Max. engine speed 4000rpm. Sent it to my local Audi dealer they told me the turbo's toast ( I have an IS20 on it ) with a fault code: 14914 P029900 Turbo/Super Charger Underboost (0110100 passive/sporadic ) Upon clearing the fault codes, the car wouldn't idle properly and the engine would occasionally stall out ( not to mention there's absolutely zero power as well ) So I just thought to install back the original IS12 turbo I had lying around.

I'm wondering does reverting back to IS12 need a retune ( or reprogram of sorts ) to run the car properly and what do I need to use back on the IS12 from the IS20?

[Traptalk]

If you needed a tune to go from the is12 to the is20 then you will probably need to revert the tune back as well

[s_uhail]

So I have a B8.5 1.8T A4 ( CVT ) Then I drove it this morning the EPC warning came on + a warning of Max. engine speed 4000rpm. Sent it to my local Audi dealer they told me the turbo's toast ( I have an IS20 on it ) with a fault code: 14914 P029900 Turbo/Super Charger Underboost (0110100 passive/sporadic ) Upon clearing the fault codes, the car wouldn't idle properly and the engine would occasionally stall out ( not to mention there's absolutely zero power as well ) So I just thought to install back the original IS12 turbo I had lying around.

I'm wondering does reverting back to IS12 need a retune ( or reprogram of sorts ) to run the car properly and what do I need to use back on the IS12 from the IS20?

What vehicle did you source the is20 from if I may ask?

I have an Is20 from a mk7 GTi but it's so different compared to the B8.5 is12 because of the longitudinal engine that I didn't even attempt to convert it

[Smac770]

longitudinal IS12 would be from the longitudinal EA888 Gen 3 1.8T, engine code CJEB.
longitudinal IS20 would be from the longitudinal EA888 Gen 3 2.0T, engine code CNCD.
So anything with a CNCD in it, which would be from B8.5 A4/A5/Q5 in relevant markets (certainly not North America).