Toyota Yaris GR Gen 1 Milltek Exhaust- Forge Motorsport FMSSXTY130MP

Milltek Sport FMSSXTY130MP is a 3-inch (76 mm), non-resonated OPF-back exhaust system developed for the Toyota GR Yaris Gen 1 (2020–2024). 

It is sold through Forge Motorsport, although the exhaust itself is a Milltek product. 

🔧 What exactly does “OPF-back” mean?

Think of the GR Yaris exhaust as:

1.6L G16E-GTS turbo → turbo/downpipe → catalytic/OPF → 🔥 FMSSXTY130MP → tailpipes

This kit doesn’t replace the catalytic converter or OPF. It replaces the exhaust section after the OPF, making it a relatively straightforward way of changing exhaust flow and character without modifying the front emissions equipment.

⚙️ Why the 76 mm diameter matters

The factory exhaust has more restrictive sections. Milltek moves to a 76 mm / 3-inch diameter, giving exhaust gases a larger cross-sectional area.

That can provide:

• Lower exhaust backpressure
• Better gas-flow capacity at high engine load
• Sharper-feeling throttle response
• More pronounced turbo/exhaust character
• Potential weight reduction versus OEM components

Milltek specifically states that its systems use mandrel-bent T304L stainless-steel tubing, maintaining smoother bends and full-flow passages.

 

🔊 Why “Non-Resonated” is important

This is the aggressive version.

A resonator’s job is partly to cancel unwanted frequencies. Removing that resonating section allows substantially more of the engine’s natural exhaust character to reach the rear.

For the GR Yaris, that means:

OEM: refined → quiet → restrained
Milltek resonated: sporty → controlled
FMSSXTY130MP non-resonated: 🔥 louder → sharper → more motorsport character

The trade-off is that cabin drone can potentially be greater, particularly at certain cruising RPMs.

🏎️ The engineering philosophy

The interesting part isn’t simply “bigger pipe = more power.”

The GR Yaris uses a small-displacement, high-output turbocharged 3-cylinder, so exhaust flow changes affect the overall system differently from a naturally aspirated engine.

The Milltek philosophy is essentially:

High-flow tubing + controlled exhaust volume + reduced restriction

rather than simply making the exhaust enormous.

A 3-inch system gives considerable flow capacity while retaining a sensible diameter for the 1.6L turbo application.

🧠 What you’re really buying

I’d classify FMSSXTY130MP as a:

Stage-1 mechanical exhaust upgrade rather than a horsepower transformation.

The biggest transformation is likely sound, flow capacity and driving character, rather than a dramatic standalone power increase.

For a tuned GR Yaris, however, the freer-flowing exhaust becomes more meaningful because the engine is moving more air and producing more exhaust mass flow.

🛠️ Installation

Forge lists approximately 1–1.5 hours fitting time. 

And importantly, the product is specifically listed for:

Toyota GR Yaris Gen 1 — 2020–2024. 

One current caveat: Forge’s own listing currently marks this particular product discontinued, so availability should be verified before purchasing. 

🏁 Enthusiast rating

Category	FMSSXTY130MP
Exhaust flow	5/5
Sound character	5/5
Weight reduction	4/5
Throttle/response feel	4/5
Standalone horsepower gain	3/5
Daily refinement	3/5
Track character	5/5
Build quality	5/5

Bottom line: FMSSXTY130MP is a particularly interesting GR Yaris exhaust because it doesn’t attack the entire emissions system—it concentrates on the post-OPF section, using a 76-mm T304L stainless-steel, non-resonated design to make the little G16E-GTS sound and breathe more aggressively. 

Toyota Yaris GR Gen 1 Milltek Exhaust- Forge Motorsport FMSSXTY130MP