'99 V40 1.6 struggling

[stevo48]

I recently purchased my V40 and have to say I am very impressed with comfort and reliability so far, the only real niggles I have with the car are misfiring under load and lack of power.
For example if I am cruising along a straight road in 4th at say 40mph and I accelerate hard the engine misfires badly and when it settles down it seems to take a long time to power up to any sort of speed.
If i accelerate hard through the gears the misfire is not noticeable and I can reach motorway speeds quite readily.
So far I plan to change air filter although it looks new, fuel filter,spark plugs, check ht leads and test coils, I will use a recommended injector cleaner (depending on what you guys recommend),also check for air leaks,vacuum pipes etc.
Any further suggestions will be welcome and duly noted.

thanks guys
Steve.

[Rooster]

Make sure its got a set of volvo plugs in it, they don't tend to like none genuine plugs