Looking for suggestions. K21L Engine 2008. Only 2 cylinders are getting spark. Will start and run on the 2 good cylinders but barely. I've replaced all 4 ignition coils and spark plugs just to rule those out. Any advice where to look next? We are located out in the country so calling anyone to come look at it requires an expensive travel bill for a tech or I have to have it towed into town. Trying to rule anything out first before going that direction. Thanks!!!