Hi all, this is the first time iv posted a question about a car so ill do my best.

I have a 2001 galant 2.5 v6 sport, it had a huge K&N cone when i bought it. After I bought it I noticed that it was running a little rough on tick over, nothing major just it seemed like it was missing a tiny bit. It was also quite bad on fuel, worse than a 2.5 should be (worse than the pajero i'd sold before it) and was running very rich and smelling like rotten eggs when I booted it. I changed spark plugs, leads and checked distributor but no change. I put it in for a diagnostic. Turns out that a previous owner had taken the engine management bulb out and chopped two wires coming off the MAF sensor. The mechanic replaced the bulb and reconnected the MAF sensor wires. He concluded that the MAF sensor was duff and ran terrible with it connected. He left it unplugged and it ran exactly the same as it did before it went in for the diagnostic (as it would), but the engine management light stayed on.
So...I replace the MAF sensor, plugged it back in and the engine management light went off. But this made it worse.
When I accelerate slowly its fine up to around 2800rpm but after that it starts making popping sounds, shudders and hesitates and i have to bring the revs back down. If i keep trying to accelerate past this or if i quickly put my foot down the car shudders for a second then the revs start dropping on their own, looses all power and feels like as if its running out of petrol until I back the revs off.
I continued to investigate. I thought maybe the huge K&N was spooking the engine management so I put the standard airbox back on and it made the fault feel a tiny bit different but didnt fix it.
I checked the hoses for any splits but they were fine. It felt to me like there was a fuel delivery problem didnt quite know why though as It run much better with the MAF sensor disconnected.
I decided to have a look at the fuel pump and then I found a frightening sight. Some one had badly added a relay inline with the fuel pump under the rear seats. now this relay was obviously no meant to be there as they had powered it directly off the battery, unfused, it had no mounts, and was connected by chopping the fuel pump wires and tape jointed the existing wires coming off the plug on the fuel pump. Tape joint on top of the fuel tank!!! thank god they didnt work loose. anyway I removed the relay as a test and it made no difference. i tested the relay and it was working fine, switching with the ignition.

I am stumped at the moment, I was thinking maybe the ecu had lost the plot or some boy racer has meddled beyond his knowledge. So if anyone has any clue your help would be much appreciated.
Thanks

 

Sorry but i dont really understand your reply ?!?!