318is performance problems please help

I used to have a 1994 316i(320 000km) very nice car very smooth at high speeds(130-200km). I recently got a 318is(140 000km) 1998 however Im very dissapointed with it. the car looses a lot of power in between 3000-4000 rpm and even though the rpm goes up the car struggles to pick up speed which is very frustrating and then after 4000rpm the car just thrusts like a turbo has engaged. Secondly the 1.9L DOHC engine is extremely rough, dont know if it is normal but it is no where near my 316i(1.8L) engine when it comes to smoothness.

I have had the car dyno tuned which increased the HP by 2-3HP, apparently it is in par with specs now, but I still feel that somewhere along the line something is wrong.

The possible problems that could be causing this problem I think is

a) air flow meter
b) fuel pump
c) Slipping clutch( the clutch is worn out)

I have done some research on forums on the internet and have come accross alot of people with this problem with the 318is. Is there a problem with the 318is I should know of, any ideas?

Cheers

Any Codes or lights on?

I found the problem, it was the fly wheel which was making the clutch sleep. I paid 1000USD just for a new fly wheel exc labour!!