The one 13mm nut under the round EGR solenoid is difficult to get at until you disconnect the hoses and EGR block first. The EGR block is attached to the rear of the driver's side valve cover with a 10mm nut and also the manifold with a 13mm nut. I got at the manifold nut with a U-joint and some extensions. Disconnect the spark plug wire loom and connector plug from the block, then disconnect the hose from the T-fitting on the firewall and the block & hoses can be pulled aside so you can get at the 13mm nut holding on the solenoid.