Got a 2wd sierra cosworth which starts cold with the normal slight piston slap & sticky tappet, But once warm and driving its fine but when under load in any gear there is a tapping/knocking noise

Now i know its not big ends as its far from that bad but just wanted to see what people think this could be ?

Its a 205 block still with dark greens, t34 turbo @ 1.5bar with chip to match, The car drives fine apart from this noise it had a oil and filter change about 500miles ago and it didnt change a thing using 10/40

Oil pressure is very good the light always goes straight out when started