I really need to get this persistant problem sorted so any help at all would be useful. Full story is:- My car (Nova Gte) drives fine when above 2,000 rpm, when im sitting at about 35ish maybe less in forth and i back off my car goes jumpy like wanting to pull forward then backing off again, It does the same in 3rd and second but only around 2,000 rpm when lifting off the throttle,the following was fitted to my 1.6 but about 30,000 miles ago, Big valve head,4 branch,K&N,air flow meter's been played with and still debate as to weather Ecu's been tampered with, Ive tried a different Airflow meter and it was even worse, Ive reseted the Ecu and still no joy, Also my timing keeps going out within a month ov being set and it idle's poor and shakes, when i get the timing done it improves the problem nut only slightly cos it runs smoother but it wont get rid ov the jumpyness, It didn't matter until now cos i used to just boot it every where to stop it happening but now ive lowered the bugger ive gotta crawl over all the speed bumps and **** and it's driving me mad jerking all over the bit.

Please help a desperate man cos it's doing my napper in and no Garage will give me a straight answer?????? HELP!!!