[Corsa C 2000-2006] 1.4 16v SRI Hesitation at Low Revs

[Hardcore]

My brother has a Corsa C, that's got an bit of an intermittent hesitation at low revs when pulling away.
There's no sign of the EML coming on when this happens or driving it at any other times.

There's a slight leak on the exhaust, near the flexi pipe. Could this be the cause? It was enough the pass the MOT and doesn't sound burst, but it's enough to hear it slightly.

He's not long bought it so fuel filter, oil filter, oil and spark plugs are on the list as it's on 92k and although drives fine otherwise, has unknown service history.

Any other possible causes, or things to check?

[Taurus]

I'd do those service items as most people selling a car don't do much before getting rid of it. Any blow in the exhaust, especially near the front end, can upset the charge into the cylinders and it usually shows more a low revs. Can he bodge it with a bandage for time being?

[Hardcore]

We've not had a good chance to have a look underneath it yet due to weather, but am i right in thinking that the flexi pipe is joined onto the centre section, rather being part of the downpipe on these Corsa's? It's going to need replaced anyway so going to factor in that with the service items and see if that helps.
It pulls fine at higher revs and checking the ecu, there are no fault codes stored so perhaps it's just overdue a service.

Will update after service and see how we get on.

[Taurus]

iirc the original system was three parts - a front pipe which included the flexi, a middle section with a box and the back box. The front pipe connects directly to the manifold. When systems are replaced different manufacturers do things slightly differently but in general the flexi is part of the front pipe section.