Downpipe Audi A5 2019 45 TFSI OPF

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Hi everyone,

I’m looking for some technical advice regarding a downpipe upgrade for my 2019 Audi A5 Sportback MHEV 45 TFSI (2.0L, 245 HP).

The car has the DKNA engine code, which means it’s equipped with two restrictive units: the primary catalytic converter (mounted vertically right after the turbo) and the GPF/OPF unit located further down the exhaust path. I want to emphasize that downpipe options for the older B9 models (2017-2018) DO NOT fit the 2019-2020 variants, even though they share the same F5/B9 chassis! Many online shops have no idea what they are selling and list them incorrectly.

OEM Part Numbers for reference:

• Main Catalytic Converter: 8W0131703AC, 8W0178DA
• GPF/OPF Unit: 8W0131765, 8W0181BA

Project Details:

• Engine: 2.0 TFSI (DKNA) with active GPF/OPF.
• Transmission: 7-speed S-Tronic DL382. I’m aware of its torque limitations, so I’m aiming for a "safe" Stage 2 around 300-310 HP and 440-450 Nm.
• Goal: I want a more aggressive exhaust note, but without the car becoming unbearably loud or smelling like raw fuel.
• Software: I already have a tuner who can handle the GPF delete and the Lambda 2 (O2 sensor) delete in the software (ECU remap).

My questions for the community:

1. Has anyone with a DKNA or similar engine successfully installed a downpipe while leaving the OPF physically on the car (either active or coded out)?
2. If I replace only the primary cat with a downpipe but keep the GPF filter physically installed (even if deleted via software), is there a high risk of it clogging up quickly and causing backpressure issues?
3. Do you know of any budget-friendly options or a custom shop that can fabricate/weld one at a reasonable price? Most "brand name" options I've found are over €700.

P.S. I’m not interested in opinions from "environmentalists" or purists. I pay my taxes just like everyone else—actually, they’ve increased despite the car being fairly new, petrol-powered, and meeting high Euro standards. I'm just looking for technical solutions.

Thanks in advance for any help!