Factory OEM exhaust
 – From catalytic converters to muffler section: 69 mm ID (inside diameter)
 – Exit (tip) diameter: ~72 mm ID
 – Upstream piping to muffler: 34 mm OD (this seems small vs cat-sections; maybe a section or branch)

Top Speed Pro-1 performance exhaust
 – Piping to the muffler: 38 mm OD, in places enlarged to 42 mm OD
 – From catalytic converters: 69 mm ID
 – Exit (tip) diameter: 75 mm ID 

69 mm ID upstream 

72 mm ID exit is ~4,072 mm²

75 mm ID exit is ~4,420 mm²

Given that the mid / muffler section is the restriction, enlarging from 34 to 38 / 42 is a significant increase (≈ 25–50 % more area). That should reduce backpressure in that region, improving exhaust velocity, decreasing restriction, and permitting freer flow—especially at higher engine speeds.

So qualitatively, the Top Speed design gives a noticeable improvement in flow capability over stock (if the restriction is indeed there), especially when valves are open or under heavy load.

Flow vs Sound Trade-offs

Increasing cross-sectional area (less restriction) tends to:

1. Lower backpressure, which helps exhaust gases evacuate more freely (improving performance or turbo efficiency).

2. Reduce exhaust gas velocity (for a given mass flow), which can reduce the “scavenging effect” at lower rpm if the system becomes too big.

3. Lean the tone (i.e. more “open roar”) and potentially more noise, especially in the audible (mid / high) frequencies.

However, because you aren’t doing a massively large oversize, the noise increment may be manageable.

Potential Gains & Practical Limitations

Here’s what you might realistically expect, given your spec change:

• Improved high-rpm / peak power / turbo response: The freed-up mid section allows exhaust gases to exit faster under heavy load. Gains might be in the single-digit percent range (e.g. 3–8 %) unless you also improve downstream (exit) or upstream (downpipes / cats).

• Better throttle response / less turbo lag (especially under load transitions).

• More audible sound under open-valve or wide-throttle, especially in the upper frequencies, but — with proper muffling design — the closed-valve mode (or quieter mode) might remain close to OEM in loudness or at least acceptable.

• Smoother flow transitions, less turbulence or eddy losses due to smoother bends or enlargements, can reduce “chugging” / resonance artifacts.

• Minimal extra noise during cruising, especially if a center muffler / resonator is retained and tuned appropriately.

Comparative Verdict: OEM vs Top Speed 

• The Top Speed Pro-1 option offers a realistic and useful improvement in flow over factory (via ~25–50 % increase in mid piping area), which should yield modest power and response gains.

• Top Speed’s additional design elements (valvetronic control, center muffler for drone suppression) indicate they are aware of the sound trade-offs and are attempting to balance performance and usability.

• It’s unlikely the Top Speed system will produce a constant massive jump in loudness over OEM in closed / moderate mode — it should remain usable for normal driving, with the louder tone reserved for aggressive driving.

• But it will be noticeably louder / more aggressive under full throttle / open-valve than OEM, which is expected and desired in your scenario.

So yes — Top Speed’s design is consistent with your goal: more exhaust flow, more aggressive sound under load, but not an obnoxiously loud system at all times.