Ive had a 620R for 7 years now . I would , in this order a) Replace your Lambda sensor. Ive only had one replacement in 7 years , they dont all fail provided b) below is set correctly. b) Check that your TPS is set correctly at load site 0 at idle and that the air flow is correct at idle.You should be aiming for 0.43V fully closed ( i e with the butterfly shut and no throttle stop in place ) , 3.39V fully open and 0.57V at idle. You will need easymap to set this correctly. These values work on my car but double check what value your map gives for load site 0 c) Upgrade your cooling system as set out in the article i wrote for low flying here here If you do this correctly you will find that your car runs pretty well on the standard map. You can then decide if you really want to spend significant sums on further upgrades ( or not !)