Disassembly:
$84/B7EF AD A4 09    LDA $09A4  [$00:09A4]   ;Load Collected Items
$84/B7F2 29 00 20    AND #$2000              ;Check for SpeedBooster
$84/B7F5 D0 13       BNE $13    [$B80A]      ;Branch to B80A if no SpeedBooster
$84/B7F7 A9 FF FF    LDA #$FFFF              ;Load 0xFFFF
$84/B7FA 8D 7A 19    STA $197A  [$00:197A]   ;Set FX3 destination height to 0xFFFF
$84/B7FD 9C 7C 19    STZ $197C  [$00:197C]   ;Set FX3 speed to 0x00
$84/B800 9C 80 19    STZ $1980  [$00:1980]   ;Set delay to 0x00
$84/B803 9C 40 18    STZ $1840  [$00:1840]   ;Set screen shake duration to 0x00
$84/B806 9E 37 1C    STZ $1C37,x[$00:1C37]   ;delete PLM (is this why it doesn't activate when speedbooster is collected in same room)
$84/B809 60          RTS                     ;Return from Subroutine (looks more like return to sender to me :P)

Disassembly:
$84/B80A AD 7A 19    LDA $197A  [$00:197A]   ;Load FX3 destination height
$84/B80D 30 17       BMI $17    [$B826]      ;Branch to B826 if height is negative
$84/B80F A9 80 FF    LDA #$FF80              ;Load 0xFF80
$84/B812 8D 7C 19    STA $197C  [$00:197C]   ;Set FX3 speed to 0xFF80
$84/B815 A9 01 00    LDA #$0001              ;Load 0x01
$84/B818 9F 1C DE 7E STA $7EDE1C,x[$7E:DE1C] ;Set PLM frame delay to 0x01
$84/B81C FE 27 1D    INC $1D27,x[$00:1D27]   ;Increment PLM instruction
$84/B81F FE 27 1D    INC $1D27,x[$00:1D27]   ;    "	 "	"
$84/B822 9E 77 1D    STZ $1D77,x[$00:1D77]   ;Set PLM variable to 0x00
$84/B825 60          RTS                     ;Return from Subroutine

Disassembly:
$84/B826 9E 37 1C    STZ $1C37,x[$00:1C37]   ;delete PLM
$84/B829 60          RTS                     ;Return from Subroutine

Disassembly:
$84/B82A A9 E0 0A    LDA #$0AE0              ;Load 0x0AE0
$84/B82D CD F6 0A    CMP $0AF6  [$00:0AF6]   ;Compare A with Samus's X position.
$84/B830 90 13       BCC $13    [$B845]      ;Branch to B845 if Carry flag is cleared (not set)
$84/B832 A9 01 00    LDA #$0001              ;Load 0x01
$84/B835 8D 80 19    STA $1980  [$00:1980]   ;Set delay to 0x01
$84/B838 9F 1C DE 7E STA $7EDE1C,x[$7E:DE1C] ;Set PLM frame delay to 0x01
$84/B83C FE 27 1D    INC $1D27,x[$00:1D27]   ;Increment PLM instruction
$84/B83F FE 27 1D    INC $1D27,x[$00:1D27]   ;    "	 "	"
$84/B842 9E 77 1D    STZ $1D77,x[$00:1D77]   ;Set PLM variable to 0x00
$84/B845 60          RTS                     ;Return from Subroutine

Disassembly:
$84/B846 BD 77 1D    LDA $1D77,x[$00:1D77]   ;Load PLM variable
$84/B849 A8          TAY                     ;Transfer A to Y
$84/B84A B9 76 B8    LDA $B876,y[$00:B876]   ;Load the value at B876+y
$84/B84D 30 1F       BMI $1F    [$B86E]      ;Branch to B86E if A is negative
$84/B84F CD F6 0A    CMP $0AF6  [$00:0AF6]   ;Compare A with Samus's X position.
$84/B852 90 19       BCC $19    [$B86D]      ;Branch to B86D if Carry flag is cleared
$84/B854 B9 78 B8    LDA $B878,y[$00:B878]   ;Load the value at B878+y
$84/B857 CD 78 19    CMP $1978  [$00:1978]   ;Compare FX3 height with A
$84/B85A B0 03       BCS $03    [$B85F]      ;Branch to B85F is Carry flag is set
$84/B85C 8D 78 19    STA $1978  [$00:1978]   ;Set FX3 height to A
$84/B85F B9 7A B8    LDA $B87A,y[$00:B87A]   ;Load the value at B87A+y
$84/B862 8D 7C 19    STA $197C  [$00:197C]   ;Set FX3 speed to A
$84/B865 98          TYA                     ;Transfer Y to A
$84/B866 18          CLC                     ;Clear Carry flag
$84/B867 69 06 00    ADC #$0006              ;Add 0x0006 to A
$84/B86A 9D 77 1D    STA $1D77,x[$00:1D77]   ;Set PLM variable to A
$84/B86D 60          RTS                     ;Return from Subroutine

Disassembly:
$84/B86E A9 15 00    LDA #$0015              ;Load 0x0015 into A (0x15 is the event bit for escaping speedbooster lava quake)
$84/B871 22 FA 81 80 JSL $8081FA[$80:81FA]   ;Jump to 8081FA (Stating an event has happened)
$84/B875 60          RTS                     ;Return from Subroutine