Car wont start right up after getting gas and runs slower

honda
s2000

#1

this problem has been going on almost since i got this car and i have no idea what it is when i fill it with gas it take about 5secs or a bit more to start up but doesnt do it after it has had time to sit but even after it has had time to sit it will get slower and slower the the more i drive it. it was bogging and chugging alot before i got the stock exhaust back on it.the car my have been flooded as well. i have replaced all 4 spark plugs, new fuel pressure regulator and fuel pump. and its still doing it. when i did the fuel pump i looked in the take there was a lil something in there but not anything that i could see that would be clogging it. anyone have a clue whats going on i am totally lost and about ready to get rid of it if i cant figure this out thatnks for your time