This is where it can get frustrating , think you've cracked it only to not gain much if anything , running good times does'nt come over night , you can have a perfectly capable motor but if the car is'nt set up right you ain't goin nowhere , big respect to the guys that run the nunbers as they've certainly earnt it.
Should of updated this before now as it may help someone else with the same issues..................
The stiff wall slicks worked wonders , the tyres must of been the problem , runs arrow straight now , anyone having issues with heavy cars then this may sort it.