Instructions
"Buoys Ahoy" Mission
Complete Bernie Crane's mission string until you reach the "Buoys Ahoy" Mission. Access the mission between 5:45 a.m. and 6:45 p.m.
Begin the mission by going south of Firefly Island to the Headland. Chase Dimitri's men after they ambush you. Stay close as you pursue them through the barges and oncoming boats. Follow them to the Steinway Cemetery, where the three men will leave the boat. Eliminate them with your sniper rifle.
Return to the boat and speak with Bernie to complete the mission. Later, Bernie will call and tell you that he got you a gift, which is an Infernus. The car will spawn at the "BC" marker on your map. Follow the marker to locate the Infernus.
Stevie's Car Collection Side-Mission
Unlock the car collection side-mission by completing Brucie's "No. 1" mission and Derrick's "Smackdown" mission. Stevie will send you a text message inviting you to acquire cars for him. He will give you a picture and location for each car. Find the cars he wants and take them to S&M Auto Sales in Bohan.
Continue collecting cars for Stevie until he asks you to steal an Infernus. Find it by going north on Montauk Avenue then north of Soldiers Plaza in Broker. It's near the Earp Street intersection.
Break the window to get inside the Infernus, then drive it to a parking spot. Return to the spawn point and another Infernus will be there.
Brucie's Street Races
Complete Brucie's "No. 1" mission to unlock the Liberty City Races. Commit to a race by calling Brucie and choosing the "Race" option.
Go to the icon that appears on the map to begin each race. Continue participating in races until your opponent appears in an Infernus.
Exit your car and steal the Infernus from your opponent. You can also locate one on the streets nearby.