The same manifold was used in MAF applications, with the addition of the MAF sensor in the air intake tube. The MAF system continued, with minor revisions, until the retirement of the engine in 2001. Ford offered a performance head that was a stock part on 1993–1995 Mustang Cobra models and pre- 1997-1/2 Ford Explorers and Mercury Mountaineers equipped with the 5.0 L engine called the GT-40 head (casting ID F3ZE-AA). In mid-1997, the Explorer and Mountaineer 5.0 L heads were revised and renamed GT40P. The GT40P heads, unlike the GT40 heads, had a very well-developed port shape/design which yielded about 200 cfm on the intake side and 140 cfm on the exhaust side without increasing the size of the ports at all from standard E7TE castings, and without increasing the exhaust valve size. They also had smaller 59-61 cc combustion chambers for added compression, and the combustion chamber shape was revised to put the spark plug tip near the center of the chamber for a more even burn. These GT40P heads are considered by many enthusiasts to be extremely efficient.