Fault Codes P300 P301 P302 P303
 

Hi all, i have a 1998 Boxster 2.5 105k on the clock CEL Light is on i can reset it but it returns

Car runs fine although sometimes it feels a little lumpy on idle, I understand these codes are a multiple miss fire on bank 1, I know all of the plugs and coil packs were replaced at 103K and I recently replaced the Lambda sensor, I reset the EMU but after a few days the light has come back on, I have a "cheapie" reader and it has this info in the freeze frame.
DTC FRZF P0300
FUEL SYS1 CL
FUEL SYS2 CL
LOAD_PCT(%) 1.6
ETC (F) 183
SHRT FT1 (%) -1.6
LONG FT1 (%) -3.1
SHRT FT2 (%) 1.6
LONG FT2 (%) -3.9
RPM (MIN) 803
VSS MPH 0

Does anyone have any ideas please ?

Thanks