Exhibit 99.4 AGREEMENT OF JOINT FILING Open Wheel Racing Series LLC, Open Wheel Acquisition Corporation, 21st Century Racing Holdings LLC, Kevin Kalkhoven, Big Bang Racing LLC, Paul Gentilozzi, Willis Capital, L.L.C. and Gerald R. Forsythe hereby...

                                                                    Exhibit 99.4

                            AGREEMENT OF JOINT FILING

      Open Wheel Racing Series LLC, Open Wheel Acquisition Corporation, 21st
Century Racing Holdings LLC, Xxxxx Xxxxxxxxx, Big Bang Racing LLC, Xxxx
Xxxxxxxxxx, Xxxxxx Capital, L.L.C. and Xxxxxx X. Xxxxxxxx hereby agree that the
Schedule 13D to which this Agreement is attached as an exhibit may be filed on
behalf of each such person.

Dated: September 11, 2003

                                      OPEN WHEEL RACING SERIES LLC

                                      By:      /s/ Xxxxx Xxxxxxxxx
                                               ---------------------------------
                                               Xxxxx Xxxxxxxxx, a Manager

                                      OPEN WHEEL ACQUISITION CORPORATION

                                      By:      /s/ Xxxxx Xxxxxxxxx
                                               ---------------------------------
                                               Xxxxx Xxxxxxxxx, President

                                      21ST CENTURY RACING HOLDINGS LLC

                                      By:      /s/ Xxxxx Xxxxxxxxx
                                               ---------------------------------
                                               Xxxxx Xxxxxxxxx, Managing Member

                                      /s/ Xxxxx Xxxxxxxxx
                                      ------------------------------------------
                                      Xxxxx Xxxxxxxxx


                                      BIG BANG RACING LLC

                                      By:      /s/ Xxxxx Xxxxxxxxx
                                               ---------------------------------
                                               Xxxxx Xxxxxxxxx, Attorney-in-fact

                                      /s/ Xxxxx Xxxxxxxxx
                                      ------------------------------------------
                                      Xxxx Xxxxxxxxxx by Xxxxx Xxxxxxxxx,
                                      Attorney-in-fact



                                      XXXXXX CAPITAL, L.L.C.

                                      By:      /s/ Xxxxx Xxxxxxxxx
                                               ---------------------------------
                                               Xxxxx Xxxxxxxxx, Attorney-in-fact

                                      /s/ Xxxxx Xxxxxxxxx
                                      ------------------------------------------
                                      Xxxxxx X. Xxxxxxxx by Xxxxx Xxxxxxxxx,
                                      Attorney-in-fact




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