please help people advice needed...

right... as most of you know my car has had a few.... minor niggles lol.

I took her to my mechanic last night who is bloody brilliant and I'd not take the car to anyone other than her, I got a new lamda fitted and on the way home the car was going like the clappers, on the way to work great again... and on the way back from work... for a while...

just on the duel carrage way I was overtaking some cars, had been doing 60ish and put her into 5th... she carried on for a wee while then she suddenly dropped the revs and started to hold back.. then from the exhaust i hear bubububububub BANG, (as if she just dumped unburnt fuel through and it went in the exhaust) she jolts forwards and then carries on as if nothing happened it also sounded like i hit the rev limiter but there is no way in hell i had (no i didnt accidentally put it in 3rd before someone says it lol)..

I had this happen before when the old lamda played up.

i carry on taking it a bit more gentle on her, when i start to get comfortable again i come to a roundabout near my home.. sitting in the traffic for a couple of mins no problem idles fine, then i pull onto the round about 1st gear fine... into 2nd.. she hesitates, then jolts forward then hesitates again then suddenly leaps forwards.. i slap the hazards on but shes fine again...

she has never stalled, i dont drive her hard, i haven't kicked the wotnot out of her and I also have only done up to 80mph in her.

I rang my mechanic and she thinks it may be the plugs and leads, but she wants to try and get some fault code readings from it. I also think personally because the car has been needing a lot of work done and now that shes running better other problems are having chance to show up.

I want to get new plugs, leads, rotor arm (bf said that bit I'm not so sure), oil change and filter and both fuel filters changed. she has already had a new rocker cover gasket, MAF sensor and idle control valve.

can anyone give advice if there is anything else I should look at? or has anyone had anything like this themselves? I'm waiting till later when the roads are quiet before i take her out again.