When you say front right side, are you referring to the drivers side or the pass side?
Lots of questions.
Do you have all the injector hard line clamps on?
Did you replace the return lines?
Did you use a lubricant on the o'rings when replacing them?
Is the cap fully seated down?
Is the hose from the IP to cap putting sideway pressure on the cap? Drivers side.
Is the hose from filter to cap putting sideway pressure on the cap? Pass side.
Are the hoses to long between caps putting sideway pressure on them?
The hard line could be cracked at the nut.
For reference, drivers side injectors are 2-4-6-8, pass side is 1-3-5-7 .