Could be a check valve located in a vacuum line.
The fuel filter on a 2003 Toyota Tacoma Prerunner 4 cylinder is located underneath the intake manifold. The fuel filter can be purchased at any auto parts store.
may want to check your air intake,filter, and the cat. converter
The 2013 Toyota Tacoma has an inline 4 engine.
The 2011 Toyota Tacoma has an inline 4 engine.
The 2009 Toyota Tacoma has an inline 4 engine.
The 2012 Toyota Tacoma has an inline 4 engine.
The 2008 Toyota Tacoma has an inline 4 engine.
The 2004 Toyota Tacoma has an inline 4 engine.
The 2005 Toyota Tacoma has an inline 4 engine.
The 2010 Toyota Tacoma has an inline 4 engine.
The 2003 Toyota Tacoma has an inline 4 engine.
The 2007 Toyota Tacoma has an inline 4 engine.