Smoothing curve with duplicate values using pchip

I have been using pchip interpolation to smooth curves plotted from data points. This has worked fine except I can't figure out how to smooth the curve when there are duplicate x values. This is what I have now:

Pressure27 = TC27Data.Pressurepsi;
Efficiency27 = TC27Data.Efficiency;

[xUnique, ia, ic] = unique(Pressure27);
yMeans = accumarray(ic, Efficiency27, [], @mean);

xq27 = [1500:.001:1250];
yqp27 = pchip(xUnique,yMeans,xq27);
plot(xUnique,yMeans,'linewidth',2);

This is mostly not my original code, I found it on this forum here.

This successfuly plots the averaged data point where there were duplicate values, however the curve that plots is not as smooth as I would like it, I want to get rid of the linear jagged edges. How can I use pchip here to smooth the curve? Thanks!