The 22-year-old right-arm quick, who has spent much of the past three years injured, took four for 41 in West Indies' 61-run victory at Edgbaston on Wednesday, a win that saw them level the three-match series at 1-1 ahead of Saturday's finale here at Trent Bridge.
That return represented career-best figures for Rampaul in what was his 19th one-day international.
His haul included the wicket of Kevin Pietersen, rated the world's best one-day batsman, clean bowled for nine as he tried to whip a straight ball legside in trademark style.
"I was just trying to bowl like any other day, bowl line and length and try not to go for too many runs, be consistent and keep the pressure on," Rampaul explained. "Pietersen was a really big wicket for me and for the team, we all know he can play shots.
"I saw him trying to chip down the wicket to me so I wanted to bowl straight and it paid off."
Rampaul, who has suffered with shin splint and groin problems, added: "After being away for so long it is good to come out and perform, I am feeling confident and bowling well.
"When I started to bowl I didn't know I would end up with four for 41 because I was going for some runs but sometimes you can't tell whether it will be a good day or bad day from the start, you just have to stick to basics and get through."
Rampaul's previous best one-day figures of two for 34 came at Trent Bridge during the last West Indies tour of England in 2004 and Rampaul was hopeful of more success this weekend.
"It is a like a final, we have to play for a win, I am confident looking forward for another good performance," Rampaul added.
"Our bowling so far throughout the limited overs series has been good, we are bowling in partnerships and we are looking to continue that on Saturday."
Rampaul added his voice to the chorus of praise for Shivnarine Chanderpaul, the outstanding West Indies batsman of this tour, who on Wednesday set up his side's victory with 116 not out.
"Shiv is the anchor of our batting and he went out there and did exactly what is required for team, he played a really magnificent innings."