Street Master Stall Converter (Heavy Duty) HT25-25LHDStreet Master Stall Converter (Heavy Duty)Suit GM V8 4L80E 91 99 Lockup With Billet Cover, 2500 Stall HT25 25LHD 25 25LHD Street Master 2200 2500 The Street converter was design for the driver who is looking for that competitive advantage. By raising the stall RPM you can eliminate that slow, sluggish start. Recommended for stock to slightly modified engines to achieve performance, along with a smooth idle when the car is in gear.