Your shopping cart is empty!
![Audi B5 S4 / C5 A6 2.7T Stage 3/4 Tune [K04/BT] (APB/BEL)](https://tunedbygts.com/image/cache/data/prod-audi-b5-s4-600x600.jpg)
GTS
Audi B5 S4 / C5 A6 2.7T Stage 3/4 Tune [K04/BT] (APB/BEL)
USD $599.99
Secure checkout
GTS calibrations are developed for vehicles with all factory emissions equipment intact and functional. Features that remove or raise factory speed and rev limits are intended for closed-course use only. These calibrations are not CARB-certified, and the customer is responsible for compliance with all applicable laws, including the emissions and inspection requirements of their jurisdiction.
The GTS difference: a real tune built for your exact car, not one calibration with three names on a dropdown. We’ve got the injectors and turbo kits to back it up, and the in-house support to actually run it. Tuning VW, Audi & Porsche since 2010.
Why we're different ›
STAGE 3: PLAIN JANE AND HYBRID K04, CUSTOM CALIBRATION
STAGE 4: BIG TURBO, CUSTOM CALIBRATION
Fits
Audi B5 S4 2.7T biturbo, engine codes APB and BEL, and the same 2.7T biturbo in the C5 A6 and allroad, with upgraded turbos: plain jane (PJ) K04s or K04 hybrids for Stage 3, a big turbo or a single turbo conversion for Stage 4. Pick your stage in the dropdown. The calibration is custom, built for the turbos, injectors and fuel on your car. Not sure which code you have? Find your engine code in two minutes. Still on the stock K03s? Start at Stage 1 and Stage 2 B5 S4.
What the tune does
Written for 93 octane / 98 RON and adapts to 91 / 95, with an E85 program as an add-on. It is built for the hardware on the car, so there is no single power figure. Lag removed, speed limiter removed, rev limit raised to 7500 with the stock head, launch control included free, and better mileage when you are not in it. Tested on the street and the track to be smooth yet powerful.
Stages on this listing
| Stage | Power | Needs | Price |
|---|---|---|---|
| Stage 1 and Stage 2 | 320 to 330 hp | stock K03 turbos | from $299.99 |
| Stage 3 | custom, built for your turbo | PJ K04 or hybrid K04 turbos, 550cc or bigger injectors, 85mm Hitachi MAF, turbo-back exhaust, front mount intercooler, upgraded diverter valve | $599.99 |
| Stage 4 | custom, built for your turbo | big or single turbo, 630cc or bigger injectors, S4 3 inch MAF housing with the stock sensor, turbo-back exhaust, front mount intercooler, upgraded diverter valve | $699.99 |
What you need on the car
- Stage 3 turbos: plain jane (PJ) K04s or K04 hybrids. The calibration is built for the pair on the car, so tell us which ones you run.
- Stage 3 fueling and airflow: 550cc injectors or bigger and an 85mm Hitachi MAF sensor. Also required: turbo-back exhaust, front mount intercooler, upgraded diverter valve.
- Stage 4 turbo: a big turbo or a single turbo conversion.
- Stage 4 fueling and airflow: 630cc injectors or bigger, and an S4 3 inch inside diameter MAF housing with the stock sensor kept. Also required: turbo-back exhaust, front mount intercooler, upgraded diverter valve.
- Connecting rods: a rod upgrade is recommended for most Stage 4 setups.
- E85: needs 830cc injectors, and upgraded rods are recommended.
After you order
- Order. Pick your stage and the programs you want, and tell us what is on the car in the order comments: turbos, injectors, MAF and fuel.
- Send or connect. Mail the ECU in and it comes back in one to two days, or pick Remote Flashing Service and flash it at home with the GTS cable.
- Build. We build the calibration for your turbos, your injectors and your fuel.
- Log. Drive, log, send. A custom calibration usually takes a revision or two to dial in for the exact hardware. Revisions usually come back the same day, and within 72 hours at the outside.
How remote tuning works, start to finish.
Options explained
- Stage: Stage 3 for PJ K04s and K04 hybrids, Stage 4 for a big or single turbo.
- E85: a program for E85. Needs 830cc injectors.
- Mono O2 / single turbo setup: for single turbo conversions. One turbo means one exhaust path, so the calibration runs on one O2 sensor and the fuel trims stay correct.
- Soft and hard launch control: both included free. Hard launch (2-step) is for off-road and competition use.
- IMMO delete: removes the immobilizer check so a swapped or spare ECU runs without the key and cluster handshake.
- Remote Flashing Service: flash at home with the GTS cable instead of mailing the ECU in.
Why GTS
Tuning since 2010, as Gonzo Tuning first and as GTS since 2013. Every calibration is written in house and the flashing tool is ours, not a rebadged package, and we never ask for remote access to your computer. Your original calibration is kept, so the car can go back to stock whenever you want it to. Reflashes carry a one-year warranty, and if you are not happy within 30 days you can go back to stock for a refund under our return policy. Support in English and Spanish.
Ordering from Canada or overseas
Canadian owners have ordered from us since 2014 and Canada is our second-largest market. The tune is delivered digitally, the cable is delivered within Canada with no customs and no import fees, we accept Canadian cards, and return shipping on a mail-in ECU is free. Anywhere else in the world, remote tuning needs the car, the cable and an internet connection, nothing else. We have tuned cars in Australia, Germany, the United Kingdom, the Netherlands, New Zealand, Hungary, Puerto Rico, Panama, Costa Rica and Barbados.