Exhibit 99.4 AGREEMENT OF JOINT FILING Open Wheel Racing Series LLC, 21st Century Racing Holdings LLC, Kevin Kalkhoven, Big Bang Racing LLC, Paul Gentilozzi, Willis Capital, L.L.C. and Gerald R. Forsythe hereby agree that the Schedule 13D to which...

                                                                    Exhibit 99.4


                          AGREEMENT OF JOINT FILING

        Open Wheel Racing Series LLC, 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: August 15, 2003

                                        OPEN WHEEL RACING SERIES LLC

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


                                        21ST CENTURY RACING HOLDINGS LLC

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

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


                                        BIG BANG RACING LLC

                                        By:     /s/ Xxxx Xxxxxxxxxx
                                                -------------------------------
                                                Xxxx Xxxxxxxxxx, Manager

                                        /s/ Xxxx Xxxxxxxxxx
                                        ---------------------------------------
                                        Xxxx Xxxxxxxxxx


                                        XXXXXX CAPITAL, L.L.C.

                                        By:     /s/ Xxxxxx X. Xxxxxxxx
                                                ------------------------------
                                                Xxxxxx X. Xxxxxxxx, Manager

                                        /s/ Xxxxxx X. Xxxxxxxx
                                        --------------------------------------
                                        Xxxxxx X. Xxxxxxxx