Pilot flying Maule M4 aircraft reported engine loss of power inflight. Performed off airport landing.

Narrative

While conducting a touch and go at ZZZ I experienced a reduction and then loss of power in my 'new to me' Maule M4 220C during takeoff initial climb before making crosswind turn. I was approximately 300-500 ft. AGL. I immediately pitched down to regain airspeed for best glide and attempted to turn towards airport. After immediately running through emergency checklist I was actuating throttle and gained a slight power response for a few seconds and then it would go idle again. It took everything I had to keep from force landing to the east of the runway. The power would go idle and I'd pump throttle and get a burst of energy for a few seconds then go idle again. I repeated this while trying to locate a safe landing spot sometimes only estimated 30-50 ft. AGL. Once to the north area of field it was obvious I would not get back to runway and the engine stopped responding to throttle inputs I knew it was time to put it down. I picked the flattest area on a small ridgeline and landed. I estimated landing roll about 200 ft. before my left landing gear caught a hidden barbed wire fence. This forced plane to go over on its nose and then upside down. We cleared the aircraft and made sure we were both unharmed. I then secured the plane and called for some help to flip the plane over. This happened on private property. There was no injury or damage to property. Once plane had been recovered I've been trying to figure out what caused the loss of power. After reviewing all ADs and SBs I then started inspecting the plane to ensure they were actually complied with. It was noted at least twice in the logs that all ADs and SBs were complied with from the seller/A&P IA. After further inspection I realized that was not true. One AD in particular AD 2003-05-01. The fuel pump that was supposed to be removed was in fact still on the plane and the cause of engine loss of power. I have attempted to reach out to seller but am unable to get in touch with him as I believe he is unavailable for next few weeks. Aviation safety at the core is about trust. Trust between pilot; mechanics; crew and all involved. I'm just a pilot; not a mechanic and I expect when a log book is signed airworthy and complied with all ADs and SBs for that to be true.