Yes they can be a pain in the ****. I think, when my 280zx injection starts to fail, ever.. i go to 2 simple carbs or Jenvey injection.. i think theire site is on www.jenvey.co.uk or jenvey.com? It's not cheap i think but you will get out of the troubles!
I don't know how much experience you have with carbs but they are fairly easy to put on the L28, and we can always help you if you don't understand the service manual. get the 240z manual and take a look at those carbs, they work also on your L28.. AND no computing stuff!! A BIG plus!! AND... if you do it yourself, you later on understand the technology and can fix all the problems that may occur! Also be proud to have done it yourself.. I was affraid to fail at making my own steeringwheel.. well now look at the little pic on the left of this reply.. (Working since 2007!)