Why is my hop up not hop up'ing

So i bought this(SRC)AEG g36 off ebay a month back and upon using it the hop up wasn't acting correct. So I took it to my local tech and asked if he could help fix it to see what's up with it. I tell him I think it's a hop up issue and it needs to be replaced he says ok. Then a week goes by and he calls and says the hop up is completely proprietary but says he'll put a new bucking and spring inside. I get it back and it shoots wonderfully. Fast forward a couple more weeks I take it out to my local skirmish field and go to chrono before the game.... and shooting 350 but hop up is completely non existent. I turn the hop all the way up and it's great BUT. shooting at 150 fps....... f**k. Any ideas of what the problem is, do j need to HPA it, does it need a nww gearbox and hop up? I know this gun is kinda dated but it's a damn G36 in the states lol and I'm the only one on my field who has one. Plz help