Will a 40bhp remap give me less lag? Or is a tuning box worth it?

Got a Vauxhall Astra 1.7 CDTI SXI (100).
Wishing to get a 40hp remap on top making it 140hp.
It's 0-60 in specs is around 11.2
How much difference will it have on acceleration and will it help with MPG (I currently get 45-50mpg with 113k on the clock)?

Or is it just worth getting a tuning box?

Thanks.

Do the remap, you'll instantly notice more power in mid range, it'll also smooth out the acceleration a lot and the car will pick up speed more easily. As for economy it depends how heavy your right foot is.

Is it worth it then? What are the downsides of getting your car remapped? More fuel consumption? How much do they cost usually too?

You get "lag" when you're not on the turbo.
Keep it spooled up and save your money.

Even with the lag it's still worth it, a 40bhp increase is hard to pass up.

It's barely enough to notice.

Nah, you'll definitely notice 40bhp above 2000rpm.

A 50 shot of nitrous only gets you a couple of tenths and a few more mph on the strip and that nets a little more than 40bhp. If you notice a poxy 40bhp you had bugger all to start with.

If it's an eBay tuning box, it definitely won't give you a 40bhp boost. Maybe 5-10bhp if you're lucky. They're not great for the engine either as they trick the ECU into adding more fuel rather than actually changing the engine map. A proper remap is definitely worth the money, but will cost you 200-300 quid, rather than the £20 that the eBay box will. However, a 40bhp increase is a 40% power bump on a car with 100bhp stock which you will most definitely notice, the car will feel like a rocket after, but this is only with a proper remap, not a 'tuning box', which as I said will do very little.

A proper remap will minimise lag, as 'lag' is the turbo not spooling up quick enough. If you tell the ECU to inject more fuel, you get more exhaust, and thus the turbo spools quicker and harder. I fitted injectors out of a 110bhp mk4 Golf TDI into my 90bhp mk3 Golf TDI and even though I only achieved a 5-10% power/torque increase, you definitely feel it in the driving. It's also a good platform for when I save up enough to get it remapped. After a remap I'll be looking at 150bhp/250lb/ft