1. Do they back up your original file?
This is non-negotiable. A proper tuner reads and saves your standard file before touching anything, so the car can always be returned to factory. If they don't, walk away.
Guide
How to Choose a Remapper
Anyone can buy a tuning tool and call themselves a remapper. Telling a proper one from a risky one isn't hard once you know what to ask. Here are seven things worth checking before you let someone rewrite your car's brain.
2. Do they diagnose first?
A health check before tuning catches existing faults so they're not mapped over. Skipping diagnostics to save time is a false economy.
3. Are they backed by a real tuning network?
Custom file development, safety validation and a guarantee usually come from a proper master-tuner relationship. We tune through the Viezu network, with files dyno-tested and backed by an insurance-backed guarantee on remapping work.
4. Will they give real figures for your car?
A good tuner quotes expected gains for your exact engine, not a generic headline. Vague promises are a red flag — try our reg-based gains calculator for honest, vehicle-specific numbers.
5. Credentials and a real identity
Look for qualifications, a real name and a contactable business — not an anonymous website. We're IMI certified and based in Chesham.
6. Reviews from real customers
Genuine Google reviews from named local customers tell you more than any marketing copy.
7. Do they talk you out of the wrong thing?
The best sign of a trustworthy tuner is one who'll tell you a Stage 2 map or a delete isn't right for you when it isn't — rather than selling the most expensive option.
FAQ
Common questions
What's the single most important thing?
That they back up your original file before any work. Everything else follows from a tuner who works carefully.
Get your free quote
Tell us your vehicle and what you're after — we'll come back with honest figures and a price. Mobile service across our local area, or visit us in Chesham.