Anything and everything Spitfire.

hi all prob a simple answer to this, bu finally got my car back on the road, its been a while and have bee sorting out those little teething problems, but took it for a test drive 2day around some country roads (nothing worse than breaking down it town) but i loose pressure on my clutch and have to crunch it into gear! it used to slip in first but thats allwayus been a prob, and i had bleed the clutch resently x2 when the pressure is there its find but its only occasionaly that i may go to pu it in fourth say and there is no pressure! but when pumped a couple of times it returns. not sure if its related but for some reason my car seems to keep backfiring and high speeds(mainly) but some low speeds too,its has seemed to have resided a bit on the journey back! but i tend to loose pressure after the back fire...i think!

any help on this would be much appreciated, i just want to enjoy my ride again!

matt