Vauxhall Astra vauxhall astra cutting out.

Hi,Ok here goes, my 11 yr old Vauxhall Astra 1.4 petrol single-point inj. has been cutting out for some time and is now getting worse. My cat was destroyed, we live up rough tracks and was replaced at garage( my 2nd cat) because I couldn't get the old bolts off, I replaced the exhaust from the cat back, replaced ignition coil and fuel filter. Took car to diagnostics to be plugged in and the fella told me he couldn't detect any faults on the circuits and in his opinion the fault was either the exhaust recirculation system/exhaust or gunk in my petrol tank.Now I've been reading a bit about similar probs and I keep hearing EGR valves? My car is cutting out when idling, going along in low gears but can cut out when getting up into 3&4 gears like it's got no power, not cutting out when it's cruising along in 5th( yet!) , it's getting so I can't drive it,the engine management lights come on, car cuts out, actually it take a little while to completely cut out and just jerks along sadly to a standstill so it's switch off wait a minute or so and it usually fires up but the engine revs sound terrible and it seems to take a while for revs to ease off on slowing down and idling when I switch it off it's like it's lacking normal power, like it's continually just about to cut out. I can only afford to run old cars and I get work done on them when it's needed and do wee jobs myself, this is worrying me as winter up here is difficult and I live up a very steep hill like 1000ft and I just know my poor car is not going to be able to keep going at this rate and I'm getting no joy at garage with this particular problem, cut out on me coming up hill today and was jerky for a time till it warmed up possibly cos it hasn't been fired up in days as I have the flu and brakes may have been sticky. Diagnostics man said he didnt think it was fuel pump, my garage says they dont think its petrol tank gunk and I keep thinking distributor, leads, fuel pump, solenoid,throttle-housing,EGR valve, sensors? etc,it definitely seems like a fuel and fuel/air problem to my amatuer car knowledge but could it also be electrical? Honestly I don't have a clue,I hope someone can help advise me, I have to get this sorted, cars fine apart from this as I just had front springs and shocks done as they were beyond it.I bought this car from an elderly man 3 yrs ago who hadnt driven it much, it has now 43,000 miles on the clock and the bodywork is good.I had the head gasket done 2 yrs ago.Oil and water are stable. Thanks for any replies any advice. Mary.