Not sure why it is spiking??? But as for the fuel cut, it doesn't come in straight away. When I first put my manual boost controller on it was running about 17.5 psi. The car ran fine, but tended to fuel cut under hard accelleration in 3rd gear, but only after about a second and then it would come back on boost again. If it is only spiking on the odd occasion you prob wont get fuel cut.....