For the cost of new Webers and manifolds, you could buy a nice used 325i motor to drop into your 323. (It bolts in, but you have to do some rewiring.) Then you'd have a reliable, modern, Motronic powerplant with 168 stock HP. (25 more than a stock 323). With a chip, it should make 180hp or so, which would be quite noticeable in your E21. Plus, it would be every day reliable with easy parts availability. Colin