I'm not sure if this advice helps front grip, but hopefully its the solution without change in springs, tyres, stabilizer. Have you consider to remove the super wide bumper ( meant for lola body ) and only use the small bumper + foam ? The wide bumper limits the front shocks travel under heavy cornering creating understeering effect. The edge of bumper hits the asphalt.
BTW, Do you loss the steering OFF power ( corner entry ), or ON power (corner exit / long sweeper) or both ? I think AFM have great expertise + explanatory solution in that matter.
If you have picture of your car naked will be great so we can look closely.